Hi Bill

Type Broadband Speed Test into Google, and choose one of the free tests to find out your download and upload speed to see if it meets your ISP minimum, (Try at different times of the day) if not get back onto them.

If it passes the above test then there is probably something running in the background that stops when you do something (Move the mouse for instance)

As Al said it could be a virus or Malware, so make sure your anti-virus program is up to date and run a full scan.

Download and install Advanced System Care http://www.iobit.com/advancedsystemcareper.html and run it, (Create a Restore Point First) as this will clear out anything left after a virus scan, as well as clean up other parts of your system. (You can also access your start up programs from within it, which is easier and safer than using MSConfig)

Finally if the problem persists, right click the task bar and choose task manager to see what processes are using the CPU resources, to see if it can be disabled.

If the above finds nothing, try a different browser to see if this works better, if not than a clean re-install of the OS will probably be required.

Hope this helps

Bill