Webroot Spysweeper is an ordinary anti-spyware program. I'm assuming that you failed to uninstall this through ordinary means. There are two approaches. The first is to
reinstall the program and then go to Add/Remove programs and uninstall it. This usually works. The second is to try Revo Uninstaller. It's a free program for personal use.
Revo Uninstaller Freeware - Uninstall Software, Remove Programs, Solve uninstall problems
Unfortunately, Revo Uninstaller also works best on programs that are installed, so you will probably have to reinstall the program and then uninstall it using Revo Uninstaller. The advantage of Revo Uninstaller is that if you choose the
Moderate or
Advanced method of uninstalling it (in Revo), it will go through your registry and strip out any remnants of the program that remain.