This has been tested with IE 5.01 and IE 5.5.  Designate one of your partitions as the master account. Get everything set up there.  Move the store to a common drive and export

HKCU\Identities
HKCU\Software\Microsoft\Internet Account Manager
HCKU\Software\Microsoft\Outlook Express

In the exported data, delete the MigToLWPVer key in HKCU\Software\Microsoft\Outlook Express\5.0\Shared Settings\Setup

Plus, make any drive letter changes you may to if the different OSes don't enumerate the drives in the same order.

Go to the new OS instance and delete HKCU\Identities and HKCU\Software\Microsoft\Internet Account Manager Import the keys from the "master" account and you should be off and to the races.

Be careful about sharing the WAB. There is currently a version difference
between IE 5.0* and IE 5.5 that will render that dysfunctional.

--Thanks to Walter Clayton, MS-MVP

Also see www.tomsterdam.com for more OE tips