Windows XP Home Foxxconn SIS661-FX MB P4 Prescott 3ghz 450w Sparkle PSU 512 DDR400 (2-256 sticks) 80GB WD Caviar 7200RPM HD 128mb built by ATI Radeon 9600 SB Live 5.1 PCI SMC NIC (brand new) Sony DVD Sony DVDRW Motorola Cable Modem w/SMC router (other computers connected are ok) The above system has been running like a champ for a year and half. Suddenly two days ago it just hard locked while downloading Netscape 8.1 (lol, garbage i know) - no mouse, no keyboard response, nothing - had to power down. After restarting it seemed to be ok while just farting around in Windows but after a few seconds of either browsing or downloading on the internet it would either: hard lock (no blue screen) or just restart. NIC, i thought so new drivers (was a 3Com card, also tried the onboard SIS900) - same problem on both - except now it would either hard lock, restart, or display and irql_not_less than... blue screen. Blue screens were far less common though and the event viewer showed nothing out of the ordinary except for terminating running programs at the time of restart. While in safe mode my system is stable as can be - surfing, downloading all ok. Things I have tried: -tried BIOS w/ fail-safe settings - same issues as above -disabled onboard devices - same issues as above -took out 3Com nic just used integrated SIS900 nic - same issues -installed brand new SMC nic, disabled integrated SISnic - same issues -tried reseating all devices - memory, ide connections, pci cards, checked for bulging or -leaking capacitators, all fans are spinning normally, temps are consistently good, voltage -reported by bios looks good. BAHHH!! ran chkdsk /r in rocovery mode - no issues ran Memtest86 for 8 hours - no issues ran Spinrite overnight - no issues ran MS memory crash anaylizer for 6 hours - no issues ran WD Data Lifeguard tools full test - no issues (system had no power issues running the above and is stable as can be in safe mode or any diagnostic I ran for a continuous hours long loop - so I don't think its the PSU?) I wiped the drive using the WD tools (all zeros full wipe) reinstalled XP - same hard lock issues. Note: install and format are flawless no issues, picks up all drivers like a champ. frustrated i actually did the same with Windows 98SE - format flawless (converted to fat32), 98 install flawless, picked up most drivers and no issues in Windows. Now, oddly win98 has not blue screened once on me. It will just hard lock or restart! sometimes after about 10min or within seconds. Another odd thing is that Knoppix Live CD 3.8 will kernel panic before booting into the os. Doesn't give me any specifics though. Guys, sorry for this long boring post but i'm about ready to throw this machine out the window - any help or guidance is greatly appreciated.