If the PC is restarting, it sounds like one of two/three things things possibly.
Bad memory stick
If you can borrow or steal a memory stick off a friend, try this first, or if you have 2 x 256mb sticks, try putting them in seperately and see if this helps.
Do you know the size of the PSU and how many devices have you got attached to the system (incl. USB)
Check your CPU temp and make sure the fan is running ok and/or try running with the case off (be careful).
DVD2one is very memory intensive, so I would check the ram out first.