Symptom:

After performing ctrl+shift+F11 (or clicking "remove accounts" in the msn installation wizard) and re-opening MSN to re-add the user accounts, the software gets hung on the first screen which says "Connecting" and the butterfly flaps it's wings ceaselessly.

Fix:

1- Go to Add/Remove Programs and uninstall everything MSN.
2- Delete the MSN core files. These are located (on XP) in C:\Documents & Settings\\Application Data\MSN6. Delete the entire MSN6 folder and all it's contents. (I'd make sure they don't have archived email before doing this, just in case)
3- Click Start, Run, type "control userpasswords2" (without the quotations. On that screen, hit the advanced tab, then hit the Manage Passwords button. Remove everything that appears in the password manager.
4- Reinstall the MSN software. They should be able to add the account back or add a new account.