Sometimes the ad-ware disguises itself dynamically in the DLL cache. It changes the names of some of its executables every time you start the PC in full windows mode making it impossible to detect, so it can re-install at next boot. You need to keep any unwanted software from running before running spysweeper etc. Start the pc in "safe mode" (F8 at boot time on an XP machine) and run spysweeper again. The fact that spybot won't run may be a symptom of whatever crap you have on your pc. It may run in safe mode. safe mode just starts the computer with the minimal software to get a display and use the keyboard/mouse, so it's a good bet when trying to rid yourself of ad-ware/spyware. Also check for add-ons under IE and Firefox. Unwanted adware sometimes installs as a "browser helper object". You can disable/delete anything that looks suspicious from there. Go to tools...add ons (manage add ons in IE)
