I don't read debug logs but here is a possibility: IF you have an AMD processor and IF you installed the SP3 update for Windows XP, that can be the cause. If you can set a time line for the problem beginning after that download and install (KB936929), uninstall it in Add/Remove Programs in the Control Panel.
The combination of an AMD processor and the SP3 update has caused well-documented freezes and reboots.
From a security standpoint, if you got SP1, SP2 and the updates since, you don't need SP3.