From the little Google searching I just did (I don't use Spyware Doctor myself), I'm inclined to think that this may be a false positive.  The program that PCTools calls Spyware.BaiDu is a BHO, and therefore should be registered in HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects, not in \Extension Compatibility\...  I think Spyware Doctor may be picking up on Internet Explorer's BHO blacklist or list of compatibility shims.