This is another one that tinkers with the Registry , but this time its on your PC and not on your device , so if you have a unlocked / locked WP7 device and want to turn your WP7 in to a USB drive this little app for your PC will do the trick. You will need to run the software on your PC ( probably with admin rights ) after your have the phone hooked up to the PC via the USB cable. Some users have reported that you should close zune for this to work and some have said this works on locked devices as well ( I have tried it on the Samsung Omnia 7 dev unlocked and it works ). The best part is you can disable this hack from the app if you dont want it.
Like all other hacks this comes with a warning : There may be side effects for using this and you are on your own and I take no responsibility if anything goes wrong. But if all goes well and you like it do shower me with thanks :) .. you should also thank the guy who made this possible MarcHoover from xda-dev
This tool requires .NET 2.0.