One of the problems with Spy Sheriff is that it's installed by a trojan, and you have to successfully remove the trojan first, then you can proceed to uninstalling Spy Sheriff from Add/Remove Programs.Here's
some information on Spy Sheriff.
You might try getting rid of it with Ad-Aware, or running an online Trend Micro House Call scan or an online Panda scan. Chances are you might also want to post a log in the HijackThis! forum here at Bleeping to see if you have any other nasties lurking.
Ad-Aware has been updated to take care of both the dropper trojan and the Faux Spyware programs that it installs, so if you don't have it, I recommend you get it and make sure it's updated. (Assuming you can still get on the internet.)