Computer lags at night?

[Alduin's Khajiit]

My laptop lags every night and I'm not sure why? beginning around 5PM my whole computer slows down and gets slower with each hour being barely usable around 11PM but if I leave it on all night while I sleep, it will be fine in the next morning at 6AM but does the same thing come 5PM the next day. the lag prevents the computer from doing most things like playing a video, mp3, or even open a folder. Firefox will blend two pages due to the lag when I switch tabs until I minimize then maximize. even typing lags.
it's like clockwork, does the same slowdowns, same degrade rate, same EVERYTHING, everyday!

I Googled the problem, found a few other people with the same issue, it was even in Google's auto-complete, not really any answers though. Can you provide any?

 

[TrainableMan]

Disconnect your computer from the internet (unplug your LAN cable or turn off your wi-fi) and see if the problem still exists. It could simply be that your various software is updating (Windows Updates, Adobe updates, Google updates, anti-virus updates, etc).

I would install Process Explorer and look to see what programs are running on your computer.

And of course, scan your computer for viruses.