Internet is running slow. what could be the cause?

Contact the service provider. Although a virus or spyware will cause this, have you run a scan for that? Also resetting the modem/router helps at times. Any downloads going on? Do you have a wireless router that is not secured? Someone could be connecting to your wireless and using it for downloads. If everyone in the area is having slow issues, could be a general outage somewhere that is causing your internet connections to be routed differently. That is usually temporary, a few hours or a day maybe till issues get fixed.