Did you try doing a full system scan in safe mode? On the Scan Page choose
Scan Options > Full System Scan. ISearch is a Browser Help Object, so here
is another way that might help in the removal:
1. Click "Tools" - "Advanced Tools" - "System Explorers".
2. In the left pane, underneath "Internet Explorer", click "IE BHOs".
You will see a list of installed Browser Helper Objects. As noted in the
key, BHOs preceded by a star should be safe, those next to an exclamation
point are unknown, and those next to a red "X" are those Microsoft
AntiSpyware deem hazardous.
Click a BHO for more detailed information if available, such as the BHO
name, description, and publisher name. Also, in the right pane, you can
choose to temporarily or permanently block the BHO. If the BHO is hazardous,
you may want to consider permanently removing it. However, for unknown BHOs,
you may want to consider only temporarily removing the object and examining
the effects later from within Internet Explorer.
How to restart in safe mode:
www.microsoft.com/resources/documentation/
windows/xp/all/proddocs/en-us/boot_failsafe.mspx
Here are some additional resources for removal:
http://securityresponse.symantec.com/avcenter/venc/data/spyware.isearch.html