There may be a high probability of malware on your PC. I have no idea of what your level of PC know-how is so forgive me if I'm telling you stuff you are more than aware of. If you want a free program that will keep your PC free of the malware gremlins please click the link below and click the Free download link:
https://www.malwarebytes.org/
These days I see so many people with clogged up computers that take an age to do anything and perform like old 486's lol, and all from clicking craftily disguised links or videos that install malicious cookies or java applets. Facebook is a good example of a main source of these nasty bits of code and it's ever more important to read everything very carefully to ensure you are clicking the right thing.
Another helpful free program you might want to try is CCleaner, this will clear out redundant files making more space on your HDD and repair your registry if there are any errors or obsolete entries, find it here:
http://www.piriform.com/ccleaner/download
Both of these will also help your games run better, if you run them regularly.
Apologies again if I am teaching you to suck eggs, but I hope this helps.