If this is appearing. Your computer is not clean.
Click here--> Bleeping Computer -> Startup Database -> PSof1.exe Information
In order for anyone to help you further. Please post all that you have done so far. Including all security programs that you have. If you have ran all of your spyware, adware and your antivirus.
Maybe you should consider posting a Highjack This Log. This link will take you to a detailed tutorial on how to post a log. How to Post a Highjack This Log
Just please keep in mind that all Highjack This Team Members are volunteers. One must practice a little patience, when waiting for help. I promise you though that they will get to you as soon as they are able.
And above all do not attempt to work on your log yourself. And only take the advice from an official HJT Team Member.
Which will show under thier name and avatar.
One more thing. Do not reply to your own post. As the Team keeps an eye out for zero
replies. If they see a reply they will assume that someone is already helping you out. Then I'm afraid that you may get lost in the shuffle.