Are you SURE it's plugged in?
That could be one of a lot of issues:
1. Are ALL drivers up to date (sound peripherals also chip set and bios updates)
2. Is your computer well ventilated and not overheating
3. virus/ male ware run them scans son!!
4. It could be one component failing- a bad stick of ram, failing HDD etc etc.
I could go on but I won't you could start by going to the windows performance and reliability monitor. There you will have a graph showing when a fault occurred and what probably caused the issue (application failure, hardware failure etc) that will give you more information on where to start looking.
There is also memtest to check RAM, run chkdsk from windows on your HDD's etc etc.
That's all I can think of off the top of my head but hope it helps.