I have a dual-boot (Leopard + infested Windows XP). I want to upgrade Windows to Vista and clean it with anti-virus. I would back up my files from Windows, but I do not want to propagate the virus. Now, I do have access to the whole Win partition from the Mac side, but I believe it is a read-only access only. Does this give me an upper hand somehow? Thanks.
For starters, a few pointers - Unless you already have paid for the licence, I would seriously look to buy and install Windows 7 instead. Also, if the machine is infected with a virus, I would have a good think about simply backing up your files and installing from scratch.
If however, I have not put you off (and again, I would really recommend it), I would follow the steps that I wrote (and others edited) in the general Anti Virus advise thread.