Lag spike

[Deathbymayo]

Lately my computer has been giving me random lag spikes and I can't figure out why.
My computers specs are an:
i7 processor
8GB Dual Channel DDR3 1600MHz
NVIDIA® GeForce® GTX 645 1.0GB GDDR5 video card
Thanks for the help

 

[Punchy_01]

Virus? My CPU was being dodgy the other day when it usually isnt. but then when i searched through files i found one disguised as a google toolbar, deleted it and it fixed the problem