i wanted to do the same and have just now figured it out.
to delete .net user accounts from msn explorer and messenger do the
following
1. create a restore point (just in case)
2. open the registry
start > run > type: regedt32
3. find the following keys:
(best if you do a search for one of the user names, as on the welcome
screen - they are all in the same hives so if you find one you find them
all)
HKEY_CURRENT_USER\Software\Microsoft\MSN6\Users\
[email protected]
HKEY_USERS\S-1-5-21-39724495-4147511435-1043117835-1005\Software\Microsoft\MSN6\Users\
[email protected]
(the long number S-1-5 ... -1005 will probably be different on your
system that's why it's best to do a search using the registry's Find tool)
4. delete the keys for the user(s) you want to delete
5. find and select the following key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
6. create a DWORD value 'DisableDomainCreds' (or modify an existing one)
and set the data to 1 (decimal)
7. close the registry and restart your computer
for more info on steps 5 and 6 visit
http://www.winguides.com/registry/display.php/1286/
it worked for me, should work for you. good luck.
have a great day.