Hi all. Here we go. I have a Compaq Presario 7940 with Windows XP Home and 512 Mb RAM. When leaving the computer on all night or for an extended period, it freezes. The mouse pointer continues to work and programs will load on occasion but VERY slowly.(e.g - 5 minutes). I have Kaspersky Anti-Virus and all definitions are current and I run a scan every day. It has found and deleted several viruses. I have checked my machine for spyware/malware using 3 programs (Ad-Aware SE Pro 1.4, Spybot Search & Destroy 1.3 and Hijack This 1.97). They all indicate that my system is clean. I have read that it is possibly a heat related or memory related problem. If heat related, why does my computer work perfectly immediately after a restart? Wouldn't the motherboard or processor still be hot? Is there and outside chance that the OS is corrupted? I have 2 fans in the casing. A 300 watt rear vent fan and the fan for the AMD-K7 Athlon processor both of which work. When I originally bought this machine, it had an OEM Windows 98SE configuration, which I upgrade to XP Home in April 2004. I obtained one upgrade for the BIOS back in 2001. There are no other upgrades available for download as far as I know. Recently I also upgraded my video driver (NVidia TNT Model 64 to the latest one, v.61.77), and also upgraded the chipset from AMD to 5.33(XP AGP Driver) In addition, I switched slots with my memory (2-256Mb cards), on the possibility of bad memory and re-arranging the memory loading priority order, and the results are still the same. Hope you guys have some ideas.