I got infected by ISTBar while searching through astalavista. I accidentally must have clicked on the "install activeX". It installs the following toolbar to all Internet Explorer windows:
I tried symantec's removal tool which said it removed the bar whereas it didn't. I had to manually kill processess, edit registry and delete files. It took me 2 hours to track the files and delete them. They were istsvc.exe, pblbpsqo.exe, istbar.exe. Later I heard of Microsoft's AntiSpyware removal tool and used to have a last clean up:
Interesting side effect of ISTBar: Word and Excel slowed down to their knees. It took around 30 secs to open a document. It was resolved after removal of ISTBar.