I have now managed to get HDInsight up and running locally on my Windows 7 Enterprise machine. A few remarks on the process that may (or may not) prove helpful to others:
It seems that ASP.NET 4.0 is needed. I did not have this and the Dashboard did not install: just three icons on desktop, just basic Hadoop running). This was not obvious to me and no errors were reported, but maybe that is just me.
I had to install HadoopWebApi and HadoopDahsboard manually as described in the thread 'Tip - Supported Windows Server versions (for a local install)'. There were two minor twists, though: the package stuff was on the E: and not C: drive (no idea why) and
the singlenodecreds.xml was in the root on C:, not in C:\Hadoop.
I had to change the Identity of the HadoopAppPool in the IIS Manager; I chose AppliationPoolIdentity but others will probably work too. I am guessing that a a local hadoop user was created on my machine but removed automatically according to the general
settings where I work. Failure to do so gave the 'HTTP Error 503. The service is unavailable' when opening the Dashboard as desribed in the thread 'Issue with HadoopAppPool Identity after istall'.
PS Sorry for not providing links to the other threads; for some reason I am not allowed to do so.
I was having similar problems and in case anybody is interested, I put together a PowerShell script to update the password and identity of the Hadoop services as well as the ASP.NET AppPool identity. The script can also switch to a different identity
if the GPO does not allow local users, but will need a small edit.