Hi guys.Maybe someone has some advice or can point me into the direction I should be going. I upgraded to a AMD Athlon XP 2100+ from a AMD Athlon 1000 which was overclocked to 1.3 Ghz on an Asus A7A266 MB. I also installed 350W power supply as apposed to my old 250W unit. I previously ran Windows XP, and Flightsim with no problems, albeit a tad slow. When I booted up originally everything seemed fine...except my startup screen wasnt showing the processor name only the frequency...I take this as the bios being out of date...so I thought I'll fix that just now. Booted XP, ran 3D Mark 2001 and it rebooted about halfway through the first test. Tried to run FS2002 and was told there was items missing from a texture file and rebooted. Windows got progressively worse...eventually not even booting into safe mode...After leaving the machine off for awhile I was able to create a boot disk, and flash the bios. The machine reconised the processor on the startup screen. As per Asus' instructions I reset the setup options to default. Booted Windows and tried again...this time I got to the second test in 3d Mark 2001 before being rebooted. Windows then gets progressively worse again, throwing up page faults on booting and not even shutting down when that option is selected but simply rebooting itself...This cant be good...If I leave the machine off for awhile it seems to work fine again for a few minutes then goes the same route...Any Ideas or suggestions woulf be greatly appreciated...Thanks in advance System Specs as follows:AMD Athlon XP2100+ (Old AMD Athlon 1000 overclocked to 1.33 Ghz)Asus A7A266 MB512 MB Ram PC13320 GB 7200 rpm HDLeadtech Geforece2 Titanium 64 MB DDR RobFAJS

Just a wild guess, but is sounds like it could be a heat problem. Does it do any better with the case cover removed? If the new CPU heatsink/fan was not installed correctly, or if the HSF is inadequate (XP 2100's put out more heat than an Athlon 1000) it could cause behavior like this.Dan

Thanks Dan I replaced the heatsink and fan and it seems to work a charm now...not as fast as I expected but it no longer hangs/reboots. Looks like heat was the problem.Thanks for all your help.Regards,Rob FAJS