If you're bringing the entire OS you should be able to ghost the old drive image onto the new drive. If you're changing configurations, this will cause winXP's copy protection to activate, and you'll prolly have to deal with Gate's cronies to get it running again.
For imaging software I've heard that Norton gets the job done.

about "My Documents"
on 16-bit windows OSes it was kept by default as a folder in the root directory
on 32-bit windows OSes it is kept in the %systemroot% directory, by default the path is c:\Documents and Settings\username\My Documents

This allows different users to have different 'My Documents' folders. So if you were expecting to see a 'c:\My Documents' on an XP install that's why it's not there

A curious part of me wonders if you could copy the entire drive from the DOS prompt. It would have to be FAT32 since there isn't much of DOS left for NTFS, and the security would be tighter. It would probably also take about a day to move that much data with algorithms designed for 60 Megabyte drives. But in the 'good old days' that's what I would have tried.