hi
there are two ways to do it
1. click on this and download TWEAK
http://download.microsoft.com/download/f/c/a/fca6767b-9ed9-45a6-b352-839afb2a2679/TweakUiPowertoySetup.exe then
Open TweakUI and click "Logon" option in the left pane. Put a checkmark against the option "Show Administrator on Welcome Screen". Click OK to close TweakUI. Logoff and see if Welcome Screen lists Administrator login. Changes are immediate and you can use the Winkey + L to switch back to Welcome Screen to see Administrator account is listed. and then click on administrator and type administrator as password
after u have logged on adminstrator, install WLM and try logging.
2. as the computer is booting press and hold your "F8 Key", u will get several options in that just select Safe Mode.
after it boots u will get the welcome screen in that Click on administrator and put the password as "administrator" without quotes.. and then follow the procedure of uninstalling and installing and log on.
lemme kno the progress