Can't really sue them I don't think. Because I think that toolbar your refering too was put there because of something you probably clicked "ok" too. The only reason I say this, is because I just took one of these stupid things that was hijacking my brothers XP machine, off........ and boy was it a pain in the rear.
It ended up that the only thing that worked real well for me was
http://mjc1.com/mirror/hjt/ << page hijacking "fix"
A great forum (not that this one isn't) that is DEDICATED to spyware and spyware removal software is
http://www.spywareinfo.com/ I HIGHLY recommend it if you run windows.
I don't run windows, but I do get paid to fix Windows computers, and that site (plus google) are lifesavers :)