Hardware

Go to the device manager and look at each device in the system. Write down the memory addresses it uses and the interrupt used. Examine written information first looking for devices that share the same memory addresses. If you find two devices that share the same memory, then look to see if they also share the same interrupt. If they share the same memory addresses and the same interrupt, you have an interrupt conflict. Change the address and the problem might go away, if that does not work change the address back and change the interrupt, the problem might go away. If not, change both the interrupt and the problem might go away. If not, change both back to original settings and do one either or both: test system devices in pairs as it may reveal the conflict, or use the selective boot (MSCONFIG) to selectively start the system devices looking for the problem to go away. If found you have your problem. Also look at the system error logs to see if they show a reoccurring error with either hardware or software because both can cause this type of problem.