Sometimes when I´m working in Premiere (CS3) my Windows (XP SP3) suddenly restarts. I cannot figure out why? It only happens with Premiere.
I remember that someone told me that this sintom occurred with him too.
Is this a conflict or some Premiere bug?
Most OS restarts that I have tracked down have been because of overheating of the system. Next, failing component, as Jim states. Could be MoBo, CPU or Powersupply. Last, problems with OS, again as Jim states.
Maybe use Speedfan (freeware) to monitor your system's temps. Within reason, you cannot run a system too cool.
NLE work is intensive and heat producting, especially at the Rendering phase. This will stress otherwise stable systems.