mrvgina.dll

Help someone please,

I installed a netgear wg311 yesterday and all was working fine i was connected and then i noticed that my logon screen had changed from the usual on winxp to a drop down box prompting for my username and pword that was fine but i wanted to change it back, so i tried to change the settings for logging on in user accounts and it told me i couldn't because of the dll file so i googled the file and someone from on majorgeeks had suggested that you change the file extension of the file to dxx rather that dll and now i cannot logon to windows at all.
After the winxp load screen finishes i get an error msg saying that the mrvgina.dll file didn't load and i cannot log on and to contact vendor.
I have contacted vendor and netgear and they cannot help all i need to do is log into windows to change the file extension back to normal. PLEASE HELP