I'm just thinking in terms of the small computer repair shop business model. If you could rebuild 3 laptops with an automated process requiring 1 man hour, it's far more efficient than spending 3 hours on each manually configuring each windows setting, all each individual app and every single driver. You could charge less per machine and create a larger customer base.
With XP, the key just has to match the OEMBIOS file set for that manufacturer (free and legal to download) so you'd just copy the OEMBIOS files for a Dell machine to the Windows folder.
Of course you have to keep your build images updated with patches but then you can just take a snapshot in VMWare (pre-sysprep), modify and save.
Computer repair is something I'd be tempted to do on the side but when I've done it in the past if I fixed someones computer once, they'd expect free IT support for life! I'm sure many of you have experienced the same.