Windows XP 32-bit has the 2GB per-process memory limit. So when on a XP system with 2GB you can run a single program/game pretty close to the maximum memory allocation, unless you start multi-tasking.

In the end I ended up getting my hands on a 4GB Corsair kit. I installed everything and several games had awful performance. A lot of stuttering, and sound "clicks". And I'm not talking resource hungry 2010 games, I'm talking 2000 games. Toughh it seemed more like drivers issues than anything else, I tried lots of Catalyst drivers and I got more or less stuttering, but alas, it was always there. So then, just for sh*ts and giggles I installed windows 7 64bits, and everything run silky smooth at 60 fps. Even games way past the time limit this machine was meant for.

All of this left me a sour taste in my mouth. I guess I'll stick with Windows 7, as it is miles more compatible than 8 or 10. I tried a lot of games from that imfamous transision time of 1999/2001 and all of them work fine, games I'm not able to run in my current Windows 10 PC.