Hi.. my system is a 6 yr. old Compaq Pent 4 2 GB with 768 Ram and XP w/SP 3...I run Advanced System Care, Super Antispyware and BitDefender 2009...I also recently cleaned out the inside of the tower, it was dusty,but I've seen worse. It still out of nowhere re-boots at times! When it does re-boot it's not as fast re-booting as it used to be, but when it's done, the computer works fine.. one time it re-booted when my son was just scrolling a sight, then it re-booted just after the screensaver kicked in..Any ideas?? Thanks!!