First you may need to disable system restore before you run a scan as it could be hiding there and re-appear each time you re-boot but be aware that disabling system restore will delete all your restore points, you can re-enable it afterwards.
Right click My Computer Icon then select Properties then click on restore tab and un tick the box.
Second you might need to use more than one tool to remove it, AdAware SE is highly recommended click here
As is SpyBot S&D click here
Also SpywareBlaster click here to prevent them getting in.
And one more that I would recommend is Ewido click here which is free to try but the only restrictions for not purchasing means you have to update and run it manually.
You must update all these products before you atually use them each time.