My guess is that your theory may be right. KG7-RAIDs run with Athlon XPs, i believe, and i don't think it's possible to safely run one without a fan or some sort of alternate cooling method.
I would get a new heat sink (with fan) and try that out.
hopefully, that would fix it. otherwise, your CPU might already be fried...
NZXT Guardian Case with Thermaltake PurePower 420w
FIC AU13 motherboard
AMD Athlon XP 2600+ 333FSB (Barton) with Thermaltake Silent Boost HSF
WDC 80Gb 8Mb cache 7200rpm
512Mb Kingston Dual-channel PC3200
MCP-T SoundStorm audio (integrated)
ATi Radeon 9800 Pro (it owned, until x800 and 6800)
Logitech Z-680 5.1 speaker system (integrated Dolby Digital 5.1, DTS, Pro Logic II decoding)
Logitech Cordless Elite Duo keyboard & mouse
Saitek Cyborg Evo joystick
Windows XP Pro SP1 (dont. install. SP2.)