Hey Hannah,
Let me start with some questions so we know which way to go.
1. Have you defraged your hard drive?
2. Have you checked your hard drive for errors?
If not, do so and restart your computer. This may fix your problem.
If you answered yes to both of these questions:
1. You have all CUSTOM windows updates?
Waiting for your answers.
Jim
(Gotcha Dale, oops!)