assuming you are a little tech savvie...
some quick tips.
1. press control alt delete on your PC, click on processes tab, and then look for exe files like search.exe, or anything suspicious. Note them down, and then search for them in windows explorer. Anything suspicious, google it and delete as appropriate.
2. go to control panel, click on add/remove programs, look through the list, and if you see any search bar apps that look suspicious, google them and then remove them.
Also, get the spyware tool as suggested. I just tend to hunt them down myself and swot them!!