I understand that you cannot sign in to Windows Live Messenger Beta version
2009 because you receive an error 81000451. You mentioned that other accounts
can sign in on the same computer. I know this is important to you so I will
do my best to help you in this matter.
We appreciate your efforts in giving us detailed problem description.
This problem occurs when the Messenger contact store is corrupted. The
corrupted cache prevents the affected account from signing in due to
conflicts between the account profile and the server. To resolve it, you need
to clear the corrupted cache files in your computer.
Please follow the steps below:
To delete the Messenger contact store, follow these steps.
Note: This procedure deletes all the contacts on the local computer. The
contacts will then be downloaded from the server the next time that you sign
in to Messenger.
1. Show (unhide) hidden files and folders:
a. Click Start, and then point to My Computer.
b. In the My Computer window, click Folder Options on the Tools menu.
c. In the Folder Options window, click the View tab.
d. Make sure that the Show hidden files and folders check box is selected.
e. Click Ok, and then close the window.
2. Delete the contact store:
The following commands delete files that you are using when you sign in and
the Contacts Cache folders.
a. Click Start, click Run, type %USERPROFILE%\Application Data\Microsoft\
and then press Enter. Delete the IdentityCRL folder.
b. Click Start, click Run, type %ALLUSERSPROFILE%\Application
Data\Microsoft\ and then press Enter. Delete the IdentityCRL folder.
c. Click Start, click Run, type %USERPROFILE%\Local Settings\Application
Data\Microsoft\ and then press Enter. Delete the Windows Live Contacts folder.
d. Click Start, click Run, type %USERPROFILE%\ and then press Enter. Delete
the Contacts folder.
e. Close the window, and then try signing in to Windows Live Messenger.
If the previous steps do not resolve or apply to this problem, you will have
to provide some additional information. You can find this information in the
Messenger connectivity log. To collect and submit this information, follow
these steps:
1. To exit Messenger, right-click the Messenger icon in the notification
area on the right side of the taskbar and then click Exit.
2. Delete the old Messenger connection log file:
a. Click Start, and then click Run.
b. Copy and then paste (or type) the following command in the Open box, and
then press ENTER to open Windows Explorer:
%userprofile%
c. In Windows Explorer, double-click My Documents, and then double-click My
Received Files.
d. In the My Received Files folder, select the MsnMsgr.txt file, and then
press DELETE on your keyboard. If connection logging in Messenger is not
already enabled, you will not see the MsnMsgr.txt file.
3. Turn on Messenger connection logging:
a. Start Messenger but do not sign in.
b. On the Tools menu, click Options.
c. On the left navigation bar, click Connection.
d. Click Advanced Settings.
e. Under Connection Logging, click to select the Save a log of my server
connections to help troubleshoot connection problems check box.
f. Click OK.
4. Sign in to Messenger again. The new connectivity log file, MSNMsgr.txt,
will be created in the following folder:
C:\Documents and Settings\Windows_log-on_name\Local Settings\Application
Data\Microsoft\Messenger\MsnMsgr.txt
I hope these steps help resolve your concern with Windows Live Messenger.
Should you have any other questions or if you need further assistance
regarding this issue, please do not hesitate to contact us again by replying
directly to this e-mail.
Thank you for contacting Windows Live Messenger Technical Support. Have a
great day.
People from Windows Live Messenger Technical Support THANKS...MSN is
working again