Are you sure about that? From what I've read I always thought that formatting would remove a rootkit virus.
That depends on where the rootkit stuffed itself.
It is true that a fresh reformat will take care of most malware, but those that also bury themselves in the MBR, take more than a format.
The MBR is outside of the partitions on the drive, at the 'beginning' of the disk.
It is this area that contains things such as your partition table, and other low-level programs, such as a sector-translation utility (which is necessary to use large hard drives on old kit that would otherwise be incapable of seeing the entire drive's available space. On-Track Disk Manager is one example of these utilities)
Any malware contained in the MBR will be executed, and in memory, waiting for your computer to boot up the operating system. Particularly nasty malware, may prevent the OS from booting up at all, among more unfriendly things, like killing the hard drive. I had one grind my drive last year until the motor gave out when I tried to remove it. I'm good at removing malware too, so this one was particularly nasty.
Go use that MBR utility posted above. Before you do tho, go into your computer's BIOS and see if there is an option that is supposed to write-protect the MBR. If it is enabled, disable it. Then run the MBR utility, and when you get your OS reinstalled, go back into the BIOS and re-enable that option. (not all computers have it, and of those that do, many still don't protect the MBR... again, personal experience)
I second the advice on Avast! tho... I use it... it is very resource-friendly. You may even see a performance boost with Trainz, without Norton anymore.
Good luck!
-- Smoovious
ps: Most of that advice is actually for Robby, not Phil. I didn't notice until I finished the post and went back through the thread. My bad.