I know that I have to back-up my game saves and othe files to an external storage device and I've seen many videos explaining how to do the upgrade.

The thing is I don't want to throw away the original PS3 HDD and I want to insert it in a 2.5" SATA to USB converter, but someone told me that this HDD doesn't work on those devices. Is that true??

just get an external usb drive, much easier... i've added a 200 gig to my 60 gig PS3 and there's nothing to it. as for the converter you're talking about, i'm not sure honestly. if i understand you correctly, you mean to conect a device that converts the sata conection to usb??? that seems pointless given the 4 usb ports on the front, again, not sure your meaning. good luck!

Yeah I guess I wasn't very clear. I just want to find an use for the 40GB HDD that I'm going to remove from my PS3, and the best one I can think of is to buy a SATA to USB converter (it is a device that has a hole where you insert the SATA HDD, so you can use the internal HDD as an external HDD). But one guy told me that the SEAGATE HDD that comes with the PS3 doesn't work with those devices and I just want someone to verify this for me.

so nobody knows huh?

well, I didn't try it yet, but as far as I know it's a standard hdd, that should work with a normal USB-case for SATA-drives ..

so, you want to take the 40 gig out, put a different drive in, then make the 40 an external drive? i get that you don't want to essentially toss the 40, but unless you already have the drive you want to put in, i still recommend going with an external usb drive to add space. as for the converter you're speaking of i can't be sure, but it should be a standard drive, so it "should" work.

If you were to upgrade your internal harddrive, I remember reading something along the lines of getting a faster harddrive (RPM) will improve loading times on some games.