I recently installed a Netgear WG311 Wireless-G PCI network adapter to a pc that was formerly using the Windows XP Fast user switching ( the login screen that allows you to simply click on your user name to login).

After installing the management software that came with it and a reboot I was presented with a standard login box where I had to type my username and password. If I tried to go to the control panel and set the fast user switching back on I received an error that stated

“A recently installed program has disabled the welcome screen and Fast User Switching. To restore these features you must unistall the program. The following filename might help you identify the program that made the change: mrvgina.DLL”

I searched around and found the following solution. Open up the register editory and go to the following key . (NOTE: always take a backup before making changes)
HKEY_LOCAL_MACHINE/Software/Microsoft/Windows NT/Current Version/WINLOGON
Then remove the key named GINAdll

The next login I was back to my fast user switching screen. 

This may not be the only way to fix this problem but “ITFIXED it for Me”.
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