Right... so figured it out (finally... not having the time to thoroughly look into stuff is a pain). It wasn't .NET.
It was a version of Visual C++ Redistrib 2005 I was missing. I happened to notice, that despite having had two installers - one labeled x86 and one x64 - and my PC showing two copies of it installed, they were both labeled x64 in the installed programs list.
Grabbed a good x86 copy from MS download center, installed, still didn't work. Ran windows update, found 1 for the new C++ 2005 install, then it worked after having done that.
Man, I got so much crap installed on that laptop at this point to support all the various stuff I run on it... C++ alone has close to a dozen different installs.... Was beginning to think I had something installed that was actually conflicting with it.