Xupiter (and it's ilk) are the enemy. Ad-Aware is your friend.
Oy! I really hate scummy programs that install themselves on your computer with neither your approval nor even your knowledge.
This morning when I started up my browser at work, I was greeted with a new toolbar that I didn't put there and that wasn't there when I closed my last browser window last night. I also had a new home page. The culprit? Xupiter, one of a string of parasitical programs that install themselves on your computer for the sole purpose of generating ad revenue for their makers or sponsors. These have been called drive-by downloads and for a good reason. Other examples are Ezula TopText, Timesink, and Gator. This is by no means a comprehensive list.
Gator is probably the most heinous of these because it pretends to have a legitimate and helpful purpose. It remembers and automatically fills in passwords and other form elements for you to save you time and effort. But it's real purpose is to load an advertising spyware module which tracks the sites you visit and pops up ads. This page has lots of good information on Gator if you're interested.
Anyway, in my fight against my new adversary, Xupiter, I turned to an old friend that I haven't seen for a while, Ad-aware. This program scans your PC's memory, registry and files for spyware/adware and can clean it up, either manually or automatically. When I installed and ran it, it found 108 (yes, that ONE HUNDRED AND EIGHT) different components of the little beasties. I told it to clean them all up, which it dutifully did - well, all except for one, which was in use. A quick boot into DOS allowed me to manually delete that file and all was well.
If you've been hijacked by adware/spyware, you need to get Ad-aware and it's companion RefUpdate, which automatically downloads and installs updates to Ad-aware's reference file, so you will always have the most up to date parasite information. You'll be glad you did. It makes cleaning up after these programs easy.