Sorry Lisa Miss this postDon't know if this will be much help, but here are a few bits and pieces you might consider.
1. According to the big players(Iomega, etc) in external HDD...booting from an external USB or Firewire drive is not possible...no model no how..at this time. Made the assumption that for all intents and purposes the new enclosure made the new drive an external usb hdd...so went looking for support info.
2. Assume that you did try to access the second drive from the administrators control panel and that you did set up your personal files with the old info, etc.....on the new install of WinXP.
3. This may be reaching a little, cause I've never heard of this being done exactly like this, but suppose you assumed that the Laptop drive was a "The old computer" and you used the transfer wizard to move the files from one drive to the other.
There are a few KB articles that address how to do this...
HOW TO: Use the Files and Settings Transfer Wizard with a Wizard Disk in Windows XP
and
HOW TO: Use the Files and Settings Transfer Wizard By Using the Windows XP CD-ROM
Obviously, I have no idea whether it will work...but...I think it may be worth a try.
There are also some administrative things for lost passwords etc that you could try...but it may be that the new install doesn't recognise the old installs files...which is why you might have to migrate the setting, etc.
Just a thought.
HTH

Adzirk