My computer has been acting starnge ever since I downloaded Limewire to my computer. I also downloaded a few sons on to my libary list.

Ever since that my computer has been acting very strange. For one it's very difficult to log on to my usual sites.

For second my computer refused to turn off last night even when I pressed the off button. After a few hours of fighting to turn it off......or get anything to happen, we had to unplug it.

How do I clean the systems out and make sure there are no viruses?