Firefox Add-on Not Removed

Spybot detected several pieces of malware on my brother's PC, running Windows 7. It said it cleaned up everything except file 121223-035237.xml, so I removed that manually. This fixed everything except one problem on Firefox (I'm still working on IE; that might still have problems).

The symptom was that there was an extra search box in Firefox marked "Search Here". It showed at the top of the window, to the right of the tabs for the pages. If you used that instead of the real search box you got sent to mysearchresults.com.

I went to about:config and found a setting for default.extension.tab (I think -- I forgot to write it down). It had the entries that showed in the bogus search box. Firefox did not let me remove it, but I could reset it to blank. But when I restarted Firefox the box was back, and so was the config entry. I finally tracked it down. There was a Firefox add-on called something like defaultsearchtab.xpi; I deleted that and the problem has not re-appeared. So it looks like the add-on was putting that setting back into the config, which caused the bogus search box to reappear.

I am sorry I did not take more complete notes, but I hope this helps.