If your PC is hooked to the internet, chances are you've already infected with malicious Spyware. Not only they invade your privacy (by sending out confidential information), they also slow down your computer in the long run.
It becomes a serious issue when credit card details and banking details are stolen.
1) Launch Malwarebytes Anti-Malware and choose quick scan to run a basic scan on common files. Or full scan if you are the more cautious type.
2) Click 'Show Results' after finish scanning to display all infected objects. Some files might be mistaken as a spyware, uncheck those files if you're sure they're not spyware.
3) Finally, click 'Remove Selected' to finish the process.