[Rockin Robbins]

First thing I'd do is a Malwarebytes scan. It's so reliable you don't even have to look at what it found: say "kill it all" and be done with it. Run the scan and eradication twice. Then go to bleepingcomputer.com and download and run ADWcleaner. It's free and finds things that Malwarebytes won't. Reboot and I'll bet it runs faster.

You could type Windows-r and do and type "msconfig." you'll get "msconfig.exe" in the results box. Click on it. Then you can go to the startup programs tab to look for programs starting with the system. You're looking for ones that are unfamiliar or those you know you don't want. Google the unknowns to see what they are. You can disable them right there in msconfig.

If your antivirus has been running the chance of a virus is low. It's much more likely that adware/spyware is just clogging the works and once it's out of the way their system will run well again.