If you truly deleted the drivers (not sure if it's possible but hey), you can probably get everything back to normal by downloading and reinstalling your motherboard's chipset drivers. That should take care of everything. Here the link, just choose your OS and click on "Drivers-Chipset", download em, and install em. USB-related stuff, among others, are generally built right into the whole chipset package so that should get everything working properly. Let us know how that works.
HP Compaq d530 Small Form Factor Desktop PC*-* Download drivers and software - HP Business Support Center