You can easily backup the entire Outlook Express folder, I've done it quite often.
Right click on My Computer and click on Explore.
Go up to Tools, and click on Folder Options.
Click on View and change to view Show Hidden Files & Folders. Now you need to refresh, or close it down and open Explore again.
Navigate to the old disk, D or E Drive and expand Documents & Settings, "User Name", Local Settings, Application Data, Identities, and keep expanding until you get to Outlook Express.
Copy this folder and if you install XP again you can paste the old folder in the new XP file once you've set up Outlook Express, if using a newer operating system, and Windows Mail, use the import wizard, in Windows Mail, to import the email messages into your new hard drive.
I would also try using the Windows repair option, on your works drive, once the drive is installed as a slave, open My Computer, right click on the PC's hard drive, properties, tools and error checking, and select the corrupt drive, depending on the operating system in your new PC.
You also mention that your works PC had 2 hard drives these weren't set up in a RAID configuration, were they?