Slow computer work

[Guest Robert]

Hello, since couple of weeks i can see very serious problem. While bit torrent is running and downloading computer slows down seriously. It happens after few hours when computer is on. Watching movies doeasn't work at all in example...When I restart computer everything is getting to normal work. My question is what makes this situation - is it made by wrong settings??? I have Vaio Intel i7, 8GB ram, 2Gb graphics....Thank you for your help