Backups for a company should always be kept off-site, or at least on an external drive not always attached to the computer. I support a company who went to a bank and got a lockbox, and they swap out an external hard drive every friday. If something really bad happens at his shop, they only lose up to a week of work.
Can you plug that HD into another working computer to pull data off of it? Don’t try to boot to it, just use it as a “slave”. If the vista cd can access the drive, another OS ahould be able to.