Yeah Stuart666, i called into PC world and requested what teh upgrade to Vista would be, OMFG!!!
I downloaded Spydoctor from PC Tools and its catching the fecker, slippery little buggers, fiesty too! Whacked the cost on the OH`s Credit Card as it was his fault for surfing some unsavory but very very interesting sites that we caught it from
Download The Cleaner V5 from www.moosoft.com. It is designed specifically for the removal of trojan horse programmes. Btw, if you have had a trojan on your system for a while, change all your passwords as most trojans are designed to steal passwords.
If the sites are as bad as you suggest, you might like to have a look at a linux live CD - this runs (as expected) from your CDROM and does not access your hard disk. Have a look at http://www.pclinuxos.com
When you have finished surfing, remove the CD, re-boot the PC and there is your Windows installation, utterly unsullied. No history, no spyware, no trace!
Hijackthis is also a good free tool. It will tell you what is running on your system. It saves a log file that can be pasted or uploaded to here and this will then tell you what is good or bad. Very handy for seeing what malware/trojans etc are actually running. Good luck.