It's what happens when you aren't grounded, there are alot of people with the same problem, but which you should try and plug your system into a grounded outlet. If that's not possible the only real solution would be to buy a USB to 3.5MM audio jack since most PC analog audio inputs are pretty awful.
If you are renting a house or in an apartment then grounded outlets are against code I believe so the building owner need to update them.