as i have recommended in another post, try setting your virtual memory to max (4096 if you are running windows xp).... to do this, right click on my computer, then click on properties.... click advanced.... then click on setttings for performace. .... click advanced in there.... then click change at the bottom.... then click on custom size, and change it to 4096 in both prompts. then click apply, and ok on the windows, your pc will reboot, and should be alot smotther. This is highly recommended for editing, because the virutal ram will not cause your hdd to thrash (which causes extreme amounts of lag when dealing with large files).... and also it will not fragment as much, and as often.
Mac G5 workstation with 4 gigs of ram, 4x250 gig drives in raid 5. High availability cluster server running centos for a server. 2xCanon GL2 cameras.