[MrMoo]

Probably not. Your not really providing enough information. Is there any similarities that you've noticed when it reboots? Like it's hot that day. You've got a lot of apps running? Your burning a cd?

Could be a bad power supply. Could be a bad cpu. Bad memory. Overheating cpu. Could be a lot.

Best guess if it's not a fairly new computer and this problem has just started happening, bad memory.