Servers: You mention that the servers are being replaced. What with? Are they being replaced with Win2K server boxes? I hope you get a transition period before having to return the old equipment.
If the servers will be running NT4, you might be able to get away with just doing a complete backup of your server and then restoring to the new server. This could also be problematic because of differences in equipment specs (which means different drivers). Your better bet would be to create one of the new servers as a BDC, synchronize with the PDC, and then promote the new BDC to PDC.
If the servers will be running Win2K, you will have to conduct a domain migration. Your best bet to do this would be to follow the last part of the preceding paragraph so that one of the new servers becomes a PDC for your NT4 domain. In order to migrate successfully, Win2K MUST be installed on the NT4 PDC.
Workstations: Much really depends on what type of ?data? you will need to move. I amnot familiar specifically with the Veritas backup product, but other backup software I have used requires either a client or agent be installed on each computer from which data will be backed up to the central backup location.
Your best bet will be to use the Files and Settings Transfer Wizard included on the WinXP CD. This wizard will help you collect the files to be transferred as well as settings such as desktop, display, Internet Explorer, etc. The wizard must be used once on the old computer to prepare everything for export and once on the new computer to import everything into the correct locations. While programs such as PC relocator will do essentially the same thing I would go with the tools Microsoft provides as they are free.
Hope this helps.