Even if the boot sector is hosed, many times you can still get the data off of the drive. If that's not possible and the drive is really dead dead, and you don't have backup copies of the needed files and drivers, then I would say that the machines are boat anchors without upgrading. But it might be possible to get original machine operating files from the manufacturer.

Also if the software will run on Win2000, it will probably run on XP also.

Just a side note, I have a backup clone HD just sitting in each one of my machines, and also another one stored off-site.