Computer Running Slow : Clicking Folders Results In Getting Properties?

my computer jams every now and again for a minute or 2 depending on what i do for E.g if i press ALT and TAB to quikly change wat im doing it jams. also whenever i click on something like a folder or shorcut of a program , instead of opening the file or folder the proprties come up ( this problem is now fixed but it might be a sympton of a virus or sumthing ?).i think its cuz of a file i downloaded off the internet.