Only when I absolutely have to. I'm not techno-crazy, so as long as it does a decent job with games, I'm usually pretty happy. I had been wanting to replace my mobo for a while, (cheapo POS ECS) so that was in the works this past spring, when the ECS decided to take a crap on me, and fried the AGP slot AND my nVidia 6800GT AGP card at the same time...SO...dumped another couple hundred $$ into a new ATI X850XT PE AGP card....Yeah, I know, if I had known in advance that the mobo AND vid card were gonna have to be replaced, I'd have upgraded to PIC-E at that time....
That will probably be my next upgrade...in a couple of years...New mobo, new processor, ram, vid card, hdd, the whole works...AND, an new PSU...hopefully, the POS Aspire 500 I have will last that long...