Computer performing slower

[Kypav]

Recently my computer has been performing slower. I used to be able to play Skyrim on ultra with some visual enhancing mods at 60fps (with vsync). Now it runs at 40 fps. It's not only Skyrim, pretty much all games in general. What should I do? I am pretty worried.

My system:
Intel Core i7 3770 @3.4 GHz
MSI Geforce Gtx 660 2gb OC
12gb ram low profile
2x 1tb harddrives
Some kind of Acer motherboard
XFX Core Edition 850W PSU
Windows 7 64bit

 

[simon12]

Check temps and background programs and if CPU or GPU usage is hitting 100%