added a 30GB hard drive to his PSP! There's apparently no size cap either, which means a hard drive well over 30GB in size can be installed. Files are accessed through the usbhost menu in iR Shell, as shown in the video below.
It's a very cool mod, but there is just one drawback. After installing the hard drive, you won't be able to access the UMD drive anymore. So if you're willing to do away with the UMD drive, then maybe this mod is for you. Enjoy!