yes they cause the reboots, but that is actually a good sign. you have reboot on error enabled by default. look on this forum there are like 3 posts people just responded to on this issue. basically right click my computer->advanced->recovery and startup->untick restart on error . this should help you write down the actual error. if it is ACPI then you might want to set your computer to "standard computer" next time you install windows 2k/xp by pressing F5 during setup.