First I want to put my hands around some necks and squeeze after a week of utterly wasted time chasing requirements not expressed in the currently untrustworthy Silverlight RC1 documentation [1,2]. All that came of this past week after searching through this forum and the web were the following references which hopefuly help explain to other victims of TS (TimeSapping) why Silverlight RC1 will not install on XP Pro machines configured with an AMD Athlon CPU.
My first lead came from Daniel Harvey on July 30th  where he explains Silverlight RC1 is dependent on specific MMX and SSE instruction sets used by the CPU for processing multimedia tasks. Apparently the AMD Athlon does not support SSE as explained at . AMD CPUs do not support the full SSE instruction set until Athlon XP (Palimino) as stated by .
Hence, it must now be determined if a motherboard which is currently configured with an Athlon CPU  may be upgraded to an Athlon XP CPU . If upgrading the CPU is possible the next seemingly impossible task will be locating an Athlon CP CPU. Maybe then Silverlight RC1 will install otherwise it seems a new machine has to be acquired to run SIlverlight. I can only wonder how many millions of people who are running XP Pro machines with AMD Athlon CPUs are going to be surprised with this dilemma?
SP2? Do you think? Already installed months ago.
Its the Athloon CPU which did not support the "full" SSE multimedia instruction set until the Athlon XP was released. Worse yet, many motherboards only support upgrading the Socket A Athlon CPU to an Athlon XP CPU if the motheboard itself met certain revision requirements. My ASUS A7133 missed by a single incremental revision my motherboard being Rev. 1.04 and the requirement for upgrade to Athlon XP being Rev. 1.05.
I have to build or buy a new computer and the question remaining is how many of the millions of other XP Pro customers are going to be "revisioned" out of the market because Microsoft's architects refused to design Silverlight so it would only fail when the particular SSE instruction sets were required. Apparently only those required to stream video.
I mean would you hire a web developer who wouldn't write validation code or whose validation code disallowed the entire application to install or continue to run because somebody entered a date type into a textbox validated for an integer?
Lots of good money being paid to Microsoft's developers producing perpetually flawed products passed on to customers and little guys who have to debug this trash at their own expense and worse yet is the @ssholes lie about it.
GO CORRECT THE PHONEY REQUIREMENTS DOCUMENT AND TELL THE TRUTH
Sorry that you had such a painful experience. We're working on getting the requirements page updated.
Nothing has still changed about the requirements doc. At least have something in the FAQ explaining that Silverlight will not work on older AMD processors. Anyway is there a workaround?
I just spent 2 hours setting up a PC to run Silverlight for Netflix Streaming...it was an older Athlon Model 4, which does not support SSE. Damn you guys!!!!!! Good thing i didn't go and buy a wireless mouse/keyboard for this specific project. It is still not listed in your requirements for Silverlight. It only says Windows XP and 500Mhz, and 128MB RAM. The PC i have is 1.5 Ghz, with 384 RAM (it's an older machine that i was just gonna use for Netflix streaming....) If you have an Athlon and can't get Silverlight to work because SSE is not working, you've come to the right place. Leave your comments and when other's google it, it will save them time. Okay.
Silverlight requires SSE instruction set support in the CPU. If you do not have SSE support in your CPU then the Silverlight install will fail and show a link that says "more information" on the installer failure screen. If you click that link it will go to http://www.microsoft.com/silverlight/resources/help.aspx?errorid=1503.
If you click that link it takes you to a page that says "Microsoft Silverlight is not supported on your computer. Your CPU does not support the SSE instruction set which is required by Silverlight."
You are correct that the posted system requirements do not say that Silverlight requires SSE support but the requirement is made explicitly clear by the installer and the help.aspx page you are directed to when the install fails.
We've gone back and forth a few times on how or whether to include the SSE requirement on the system requirements - the problem is that the vast majority of people do not know what SSE is or if their CPU supports it. So saying that we require it up front would confuse far more people than it would help. MMX was touted a bit in marketing docs when it was released but inconsistently but by the time SSE (and SSE2, ...) instructions sets rolled around they are rarely mentioned anywhere. So most users that check the sys reqs before installing and see SSE is required will likely either think that they don't have it when they do or at least ask the next logical question which is "how do I know if my CPU has SSE support?"
I guess I am still missing it, I have a Athlon XP 2600+ (I also tried a older Duron 1200) 512 ram XP sp 3 media player 11 IE 7 and I still am getting a cpu not supported message. From what everybody else is saying the processor should work. Is there a silverlight compatible plug-in out there that will work?
I've seen a few reports where a CPU that definitely supports SSE doesn't return true when the Win32 function to check for SSE is called.
The SSE check is done in the Silverlight installation executable which wraps the MSI install. You can extract the MSI and MSP from the exe and install using msiexec.exe. Note that if your CPU doesn't support SSE and you install in this manner and run Silverlight applications your browser will crash when Silverlight runs SSE instructions (that's why we block install if we don't think your CPU supports SSE).
To install using msiexec.exe, download the Silverlight installer (uninstall Silverlight, restart your browser, browser to www.microsoft.com/silverlight and click the link to install Silverlight then save the exe instead of clicking to run it) and then run it from a command prompt with the /x argument. If you are on Vista with UAC enabled, make sure that you run the command prompt as an administrator (elevated). Running with /x will prompt you for a location to extract to - enter a temp path such as c:\sltemp. CD to the c:\sltemp directory in your command prompt and run "msiexec.exe /i silverlight.msi" to install the baseline followed by "msiexec.exe /update silverlight.msp" to patch it to the current version.
As I said above, if your CPU doesn't support SSE, don't install this way. Silverlight really does require SSE so circumventing an accurate check for SSE support is not going to help you. Executing CPU instructions on a CPU that doesn't support them is nothing but a quick way to crash.
If you follow these instructions and Silverlight crashes - you probably don't have SSE support. Uninstall Silverlight to make it stop crashing.
2009 0719 I just came across this today as the Netflix push for the new Silverlight plug-in hit my account/computers. As lchamale suggested, I thought I would leave a comment to help others in the future searching for information. I too have an AMD Athlon 1.4 GHz processor in one of my older machines. I received the same SSE message mentioned in the prior posts above. I tried to call the Microsoft phone number the Netflix customer provided but it seems I have to call during their normal business hours. I expect no resolution but will post if there is actually a resolution they can provide. I haven't tried what rpomeroy provided yet so no info on that either. Glad I found this though. Thanks!
I ended up here, because MS is nixing the Investment Software Toolbox on MSN Money.
The replacement will require Silverlight. But, I have an AMD Sempron 3400+ processor.
Tried to find complete set of system requirements for Silverlight. Not available.
Looking at this AMD incompatibility, it begs the following question : How much of a "Consulting Fee"
must Intel have paid to Microsoft to make Silverlight incompatible with AMD processors ?
I simply can't find any other reason. Consider that the HP/Compaq computers w AMD processors do hold a significant
market share. For Microsoft software engineers to act as "Software ***" ("Garr, no Silverlight for you!!")
with regard to AMD cannot make sense, unless they got paid extra to act mean and stupid.
Shame on MS and Intel! If I were a government lawyer (Commerce, SEC, etc) I'd investigate this.
This type of collusion is not that far-fetched, if you know how MS acted in prior competitive disputes.
Simply put, if you go to a gas station, and they tell you "You can't gas up here, unless you also
buy a coke, and fries, and you can only buy a coke, if you agree to get a new transmission right here, plus we
will smash you radio, and you need to buy a new one from us, and will tell you which movie you can watch, etc.".
No one should have to put up with this kind of overbearing behavior.
Well, so I have to live without silverlight. Sigh!
The Sempron 3400+ should have SSE support.
Also, for what it's worth, requiring SSE is not really an Intel vs. AMD thing since both processors have SSE support though it may seem that way from this forum thread. The reason that most people running into the issue are on AMD is that Intel added support for SSE first such that you're more likely to find someone keeping an old AMD that doesn't support SSE running than an even older/slower Intel box.
Does install fail saying that your CPU is unsupported (if you click more information when install fails, does it go to a page that says SSE support is required)?
If so, you can try the workaround I posted above of extracting the msi & msp and running them with msiexec to circumvent the check.
Also, FYI to anyone that is interested in how our check for SSE sometimes fails on certain AMDs that definitely support SSE, all we do is call the following during install:
[.. code that logs the error and returns the error code removed ..]
Per http://msdn.microsoft.com/en-us/library/ms724482(VS.85).aspx this is checking for MMX and SSE support.