"Using XP-lite - design yourself the leanest XP-build possible - and then run that as a virtual OS inside Win 7 64-bit."
Are you talking about virtual computer? I use VMWare Workstation but graphics aren't so good. workstation
Started experimenting with virtual computing about 2007 and I wish I could figure out how to implement my own graphics drivers into this software. Had XP 64 bit as my OS (and every other OS (Windows only, no Linux, Ubuntu, etc.) Used Demonoid to find em. Demonoid is back by the way, Finding the serial key was difficult for some as VMWare wouldn't let me skip it to activate it later. Overcoming the problems was half the fun. lol. I started messing with these things back in 2000 when i noticed a recycling center had a dumpster full of trashed computers and the dude let me load up my truck... the rest is history...self taught.
SSD's are a great help to play WGT also.
If I'm not mistaken from what i read, Win 10 will be mandatory soon.(I don't see how since many,many users still have XP and 7}
I did manage to go into the background services and turn Windows update to "disable" to thwart that attempt by Microsoft . Win 10 says you can turn it off but if it stays off, they will turn it back on for you. (imagine that!) here's the article i read about WIN 10 ...
http://www.forbes.com/sites/gordonkelly/2015/10/30/windows-10-upgrades-now-automatic/2/
http://www.forbes.com/sites/gordonkelly/2015/08/26/windows-10-how-to-stop-forced-updates/