I guess I should have given more indepth info on my system, so here it is. Celeron 900, ASUS TUV4X mobo, SB live 5.1 sound card, and GF MX2-400 video card. I reinstalled my memory DIMMS, and actually until I get an idea of what the problem is I'm only installing 2x256 for now. The system recognizes all the memory at post, but when it's running and I check my system in control panel, it only says I have 511 installed. No errors come up, but it hangs once in a while. Sorry for not telling all of this the first time, but I'm new at this. Once again any help would be appreciated.