not a dig or anything but 8GB for any home PC is wayyyyyyyyy OTT. Even 4GB is a bit much really. I used to run 1GB on XP and was fine. Then went to 2GB now got all four sticks run dual channel interleaved on 3GB and is probably as much as I will put in my PC. On my memory monitor the absolutely MAXIMUM it ever uses is about 49-50%

And edit I'm running Vista 64Bit which is an even bigger drain than XP is