May not be a driver
problem if everything in the device manager shows up correctly.
Have you run Windows Defragment Utility and do you Defragment your hard drive on a regular basis (once every two weeks)?
Have you run a Spyware/Malware Scan, being infected with Malware/Spyware can slow down you system severely not to mention puts your system at a security risk.
Here are some good free maintenance/security programs for Windows 7: Malwarebytes.org CCleaner - Optimization and Cleaning - Free Download