A good place to start is to check your profile. Have you got administrative privelidges on that PC. Open C:\documents and settings.

Select the folder called your user name. Right click and choose properties. Security tab and advanced. In the owner tab make sure your name is selected, if not select it and check Replace owner on subcontainers and objects.

Then make sure you have full control on the permissions tab, and check "Replace permissions entries on all child.........."