system
24
Any up to date security is going to have problems on 256, if not now then soon.
I have a 256 machine…one of the only things I can stomach running on it is Puppy Linux, so I can imagine XP would have probelms. 
The time has come for you to invest in some RAM, imo. Cheap to buy, easy to install…unless you are just having so much fun on 256, you don’t want to leave (doubt that). ;D