DON'T DOWNLOAD IT!!! It's a con.
As suggested above, download and install Adaware and Spybot (both free). I also use Spyware Blaster and Windows Defender (both free too).
Once the programs you want are downloaded and set up, boot into Safe Mode and then run their scans - you'll have a much better chance of removing any nasties in safe mode.
If you're REALLY unlucky it might be a bit more complex than running the above progs, but 9 times out of 10 they should do the job.
PS Zone Alarm is also a good free firewall (I found Comodo a bit too verbose for my liking, though I didn't spend much time with the options).