Well, ususally you can remove drivers by Windows 7 by getting up Device Manager in Control Panel (or by right clicking Computer icon on the desktop and choosing Properties then get up Device Manager).
After doing that you go to your Sound Unit and look at the drivers page and see what version you have listed by Windows 7. Then you un-install the entire unit out of the computer and when the screen comes up, you check to un-install the drivers also. When you restart your computer, if you have other older drivers still kept in Windows 7, Windows 7 will automatically install those drivers, and you do the process over again, until Windows 7 can not find any drivers to automatically install. Just some things in Windows 7 are annoying to me at least in my opinion.
Revo Un-installer can just look at your system and you can do all types of maintainence on the computer and check if any program was a program that did not un-install everything (which they always do) and delete it completely out of the OS system and computer. It cleans up the computer with various tools, although I can say if you do the HardDrive bit of deleting files so you can not ever find them again, it may take you a couple of days, because that will take a long time. Kind of a sparkly clean computer in a few days if you do everything. I could not wait to really clean up the harddrive by thoroughly deleting files instead of Windows 7 just marking them as deleted, but if I have some time I may try that even.
It is all designed by Microsoft to make it seem as if the computer is faster, and it is just tricks in the end (like the harddrive really never really deleting files just marking them as deleted and the harddrive is used over again - of course that works, but then...................it is not sparkly clean on the harddrive then).