Windows

Rename the "Main Identity" Subkey
Before you back up the Identities subkeys, you must rename the Username value of the Main Identity subkey. To do so:
Click Start, and then click Run.
In the Open box, type regedit.exe, and then click OK.
Locate the following registry subkey:
HKEY_CURRENT_USER/Identities

To do so, in the left pane, click the plus sign (+) that is next to each registry key or subkey in the path to expand each branch until you locate the subkey that you want to delete. For example, in the following registry subkey path, the subkey is Identities:
HKEY_CURRENT_USER\Identities

In the left pane, click the plus sign (+) that is next to the Identities subkey to expand that branch. Note the globally unique identifier (GUID) subkeys; each is named with a unique ID number, such as the following:
{AFE1AA0D-D202-4C52-AC8D-F68DE06421C1}

In the left pane, click each GUID until you find the Username data value Main Identity.
In the right pane, double-click Username.
In the Edit String dialog box, type Main Backup in the Value data box, and then click OK.
Back up Individual Identity Subkeys
For each identity that you create in Outlook Express, an entry is automatically created in the Microsoft Windows registry. Back up these identities before you delete the Identities subkey. If you do not, you may be unable to use your current identities or shared contacts after you restart Outlook Express.

To back up your identity information:
In the left pane of Registry Editor, click the Main identity subkey.
On the Registry menu, click Export Registry File.
In the File name box, type the user name for the identity. For example, if you export the Main identity subkey, type Main.

For additional information about how to back up Outlook Express data, click the article number below to view the article in the Microsoft Knowledge Base:
270670 OLEXP: How to Back Up and Recover Outlook Express Data