Windows XP seems to relinquish resources on my 512MB (don't ask why it is so low, also notice I used the big B as in Byte) laptop, allowing me to play The Sims 2. No complaint there.
In fact Windows XP seems very well behaved at most things. The complaints usually come from 3rd party items,
a) Crapping files all over the place and 'not' cleaning them up at uninstall.
b) Accessing the hard drive at random times or not efficiently resulting in a 'slow down'.
I could also complain about Media Player and IE, but I'm not forced to use them.