Computer incredibly slow after CPU-fan cleaning

skillns

Commendable
Sep 17, 2016
1
0
1,510
I'm not a very PC-savy guy, but I tried my hand at cleaning my pc. In the process I removed the CPU fan from the CPU, seperating the heatsinks. Being an idiot, I didn't replace the thermopaste (have now) but I'm quite sure I'd have smelled the smoke if it was burnt. Have no clue what may cause this, please help!

With simply Chrome running my CPU usage is at a steady 50%-ish.

The CPU is an Intel Core i7-4790K CPU @ 4.00GHz.
Can provide pictures if need be.