Windows XP rebooting at startup

[Haal]

I have XP Professional SP2 on my computer, and it has started to
reboot at startup. Right after the boot screen has finished to
load, I notice my hard disk going in standby and the system reboots.
I tried to boot in Safe Mode, Debug Mode and other options, but none
of them worked.
This problem has started occurring about 2 months ago, so I had to
use my second installation of Windows XP sp1 on the second partition.

How can I solve this problem?

 

[Guest]

So you have one working copy of XP and one bad copy of Xp.

do a"Repair Install" on first copy of XP.