I just picked up DDR2 667mHz 2GB stick for a NOTEBOOK for $35. You'll find something on the cheap. Just make sure it's quality. I paid $10 for a noname memory awhile ago and i could barely load windows w/ it.
ya my wifes pc was blue screening alot, turned out the budget ram was at fault.Got some good quality ram on sale (love ncix) and it has been very stable.