The BCD registry file is located in the \Boot\Bcd directory of the active partition.
In both cases you'll have to locate your BCD file. On the other hand, if you have a Windows CD or USB, you can also use bcdedit /deletevalue safeboot after you've booted into Recovery Environment. There are tools for Linux which can edit BCD like hivex (very hard because you'll have to understand the structure) or EasyBCD which seems easy enough. Newer versions of Windows use BCD, which is basically a registry hive. The above is outdated (apparently since Vista). Assuming you can log in again (which your last comment implies): Either start 'System Configuration' again and disable safe boot there or, if that doesn't work, edit C:\Boot.ini and remove /safeboot or /safeboot:networkthere.