A SharePoint user in Company XYG changes her name, sends a request to get the name changed in her Exchange Account and her Active Directory Account. IT changes name, but name shown on SharePoint user logon displays her old name.
Use the STSADM command line "Migrateuser" to change her details.
1. Log on to the SharePoint web front end with user having Farm Admin rights
2. Open the Command Prompt
3. Set directory to 12 Hive. C:\program files\common files\microsoft shared\web server extensions\12\bin
4. Run command stsadm -o migrateuser -oldlogin domain\olduseracct -newlogin domain\newuseraccount
5. Voila! User Account changes is updated in SharePoint
Applies to WSS 3.0, MOSS 2007 (might be the same for SP2010)