Why do you even speak? Can you give us details on the hardware you have? Power supply, motherboard, processor, memory, hard drive, etc? Typically when a computer reboots and cannot keep the proper FSB speeds, there is usually an issue with the processor itself. Though this is not necessarily the case. There are a number of things that must be checked. One of the most common oversights which can cause a multitude of problems is congested fans. Open up your case and take a good look at your CPU fan, make sure it's completely free of dust. To clean it, if necessary, simply blow on it, use a dry paint brush or use a can of dry compressed air. There are a number of other things to verify as well, however without knowing what your specific hardware is, it's hard to know where to go.