Damien, first port of call would be HijackThis. There is an online analyser
here.
If you have no luck with that, in an
old thread I recommended a tool called 'ComboFix' from the Bleeping Computer site - that worked for COL.
If your data is on a second drive, reinstalling Windoze should not affect it, other than having to reinstall any progs that use the data. If in doubt, unplug the second drive while reinstalling. However, are 100% certain the trojan isn't hiding in the data drive.
PS - don't forget to disable the system restore points while trying to clean the trojan - they love to hide in there.