Could you please be more specific by what you mean by "crashes"? Do you get blue screen of death? A particular application or process having an abnormal termination? Total system lock? If it's anything other than total system lock, does Event Log show anything? How long has it been doing this for? Since Day 1, or only recently. If it was recently, was it immediately or almost immediately after making a system change, such as new hardware, installing software, driver update, Windows patch, etc?
If the system is just outright lockin, especially if nothing changed before it started, you most likely have a hardware problem. The best way to track that down is to try swapping the RAM first, if that doesn't do it, put the old RAM back in, swap the CPU. If it's still locking, put the old CPU back in and swap motherboards. It may also be a driver issue on an outright lock, but my experience has been that it's usually a critical hardware failure such as bad RAM. If it typically happens during disk-heavy activity, I'd be especially suspicious of the motherboard.
Since it's happening with a wide variety of software applications and functions, it probably is not a particular application causing it.
J.Ja