It amuses me that you would use that phrase when you are the one citing the golden age of modding and how it was so much better under x, y, and z circumstances. Garry owes you nothing and he has a right to do what ever he feels like with his work. You want to give your work away for free...
That was probably a bad idea. A lot of your software will not work because when you installed them they were under a different OS. Same thing happens with all but the most basic of apps when going from say Win98 to WinXP. My advice: format and do a clean install of WinXP64.
Regardless of how antiquated HL2 technology might be, HL2 runs better on my system than either FarCry or Doom3 and last time I checked Quake4 still uses 2d skyboxes. Perhaps you should get onto Raven about that.
The SDK is completely in VS .NET which means that if you want to use Borland or anything else you have to re-create the project files which would suck to do.