The links the others have mentioned will help, your homepage has been hijacked. For more advice and details of what others did to resolve this problem just use the search on the left hand side and do a search for hijack.
I had the Mysearch prob too Chippo, it was a right pain. I tried sorting it with Spybot, Adaware, god knows how many virus scans...still had prob. Then i happened to notice...at the very bottom of the Mysearch webpage it had (in very light blue and quite tiny) *problems?*
Clicking it took me to a page that gave instructions how to stop being sent to the Mysearch page all the time (i was like *do i trust this??*) had nothing else to lose so trusted it...and it worked!