Need Help Memory partition Deleted!!!

Hi

A friend has a psp, and a 2gb memory stick pro duo. he tried to use a pandora battery to mod it, and he made a "magic-stick" from the memory stick.

somehow, he stuffed it up, and the psp freezes at startup. but thats not what i want help with

i was trying to make him a new magic stick, and i deleted the partition on the memory stick. now the psp wont see the memory stick, and windows wont allow me to make a new partition. (it does come up in my computer, but if you click on it, it asks for you to insert a disk into the removable drive.)

anyone know how can i fix this?

Thanks