This has been posted before...
Delete the Lockdown folder. Open iTunes.
- Windows XP:
C

Documents and Settings\USER\Local Settings\Application Data\Apple Computer\iTunes or C

Documents and Settings\USER0\Application Data\Apple Computer\iTunes
- Windows Vista:
C

Users\USER\AppData\Roaming\Apple Computer\iTunes\ or C

Users\USERS\AppData\Apple Computer\iTunes
In XP the mentioned folder is a hidden one...
Set your folder options to display hidden system files and folders...
That way the folder...though greyed out..will became visible...
Goodluck !!!
Cheers...
Wallyİ...