Complete Crash of computer, no BSOD what so ever

A few months ago my computer of a year started having an issue of crashing, and not normal crashes I am used to. There has not been a single BSOD occurrence once these lockups and crashes started happening.

The order in which things go:
-Normal activity on computer
-Cursor freezes, cannot move
-Check CPU gadget, shows CPU processing spikes
-Cursor freezes again, happens repeatedly, at about 5 to 10 second intervals, each showing a CPU process spike
-Attempt to open up task manager to get a better look at processes, computer locks up, goes to black screen, video output soon shuts off, shows that there is no video input to monitor, computer still on
-Happens maybe once a day, some days up to three or 4 times in a day
-Some occurrences I will not move into task manager, see if it will quit on it's own, will continue to freeze every 10 seconds or so at about 5 seconds freezing time, eventually it will crash on it's own


I have not installed any new hardware to my computer, and only recently have I installed more security on here (Microsoft Security Essentials), that being the only thing. Started happening up and out of no where, any advice would be much appreciated!