yes. there is a way. there is a down part though. you have to format your external hard drive into FAT32 (same as a usb) you dont have to format the whole thing just enough. the other downfall is you have to backup the ps3. which means if you want to give the game to someone they will lose all their game fils (unless they copy all saved game files onto a usb) but they wouldn't be able to receive trophies if they use saved game files. you just back up the ps3 onto your hard drive it will save user accounts, photos, messages that werent deleted etc.. i have tried this before but only on my own ps3 i havent tried it on some one elses.
i hope this helps answer your question