Girlfriends computer not booting

[sic6six]

ok im at my girlfriends on her laptop. reason being is her pc is playing up. it only just started today. she is running windows xp home on her pc using sata hard drive. when you turn on the computer it freezes at the post screen and has to be turned off and back on again. it says her cpu isnt running at the corect speed on her bios when you turn it back on which is confusing as the fan is working fine. we have tried several attempts to fix the problem but to no avail as it throws the same fit evey so often and we have no idea why, or what is causing it. can any one help please

 

[Explicit]

Tried clearing the CMOS?

 

[sic6six]

wo dont suspect it to be the cmos. she has just removed all her cathode lights and it seems to be working now. sounds a little peculiar that the lights would be the cause. she has also borrowed a copy of windows server 2003 from college so she can get some sceenshots done for her work but has had no luck installing it on a sata drive. any idea how she can get it install on there