In your F:\ drive will be a tool called the "build uninstall wizard" under the path: F:\Setup Tools\Build Uninstall Wizard\sqlbuw.exe
Run this tool and see if it detects anything and removes the components. I really don't know exactly what you deleted in terms of random reg keys and directories, but somehow there are components left behind that setup is detecting.
As for your most recent error you encountered, that means there was another windows installer package running at the same time and setup was in contention with that and error'd out. I bet if you run it again you won't get that error. Usually that happens if windows updates are installing.
Thx... Niko SQL Server Setup Team
WISHLIST: Why cant you run the command installer in Vista, then see the comments column in order to MSIZAP stuff anymore?? That was a cool feature, especially for products like Visual Studio 2003...