|Almost certainly you had a pop-up from a bogus AV (a virus) that said you computer had multiple infections. It hadn't but by clicking on it you have now. This is widespread and quite frequent.|
NEVER click on a popup of that type in future (don't even close its Window). You either End Task using Ctrl-Alt-Del keys or you reboot, preferably both. If you have CCleaner on board run that too.
After taking the advice already given in #1 it would be worth downloading, updating and running MalwareBytes free version to see if that can find anything else.
How to know you are getting old 3:
You start converting your age to hexadecimal