Why not open it? If after some attempts there is no way to make it work, the next step is to open and try connecting the disk inside the computer. If the warranty has expired, as I guess it is, then there is nothing to keep him from opening the enclosure. Then, he can buy a new USB enclosure, if he wants to use the disk as external. But I would thoroughly test the disk first to see if it is damaged or not. The Seagate tool to test a hard disk and even attempt to fix some bad sectors, is SeaTools. I have Western Digital Lifeguard Diagnostics which I use for quick or thorough test (sector-by-sector) of any brand drive. However it is recommended to use manufacturer's own utility (in his case Seagate) because a foreign software won't attempt to fix bad sectors, it will only test the drive.
After finding out that the drive's health is OK or is fixed, then he can buy a USB enclosure to make it an external disk again. Otherwise, he can keep it for temporary use (transfer files between computers) as I explained in my previous post.
PS: Some bad sectors can be fixed by writing zeros to the drive (low level format). This of course means that he must first backup all data to another drive and then let it several hours to complete. If writing zeros completes successfully, then the drive should be in the factory unformatted state. So he can format it again and use it.
Even though it seems to be a widely used term, writing zeros to the drive is NOT the same as low level formatting. Low level formatting requires special equipment and cannot be done on modern drives. Older MFM drives used to have a low level format program built-in to the firmware on the controller, had to boot to a DOS prompt and use the DOS debug command to do it, at the Debug prompt you had to enter something like: G=C800:5 to start the format.
Well, shoot. If we're going for one upsmanship (downsmanship?) the first PC that I owned was a 128k toaster Mac, purchased in October of 1984, plus an external single sided 3 1/2"400k floppy drive and an Imagewriter dot matrix printer (made by C. Itoh). I haven't yet forgiven Steve Jobs for going to market with such a worthless toy. (The 512k Fat Mac was actually usable.) I didn't go over to the Dark Side until 1995. All of my PCs have been homebuilt since 1997. It's amazing how little you need to know to slap a PC together and get it up and running with modern Windows (95, 98, NT, XP, Vista, 7, 8, 10).
On the work-related side, things go back further. IBM 2741 terminals communicating with an IBM 360/370 at less than 150 baud to run APL. Hollerith cards read at an RBT for a CDC 6400 (later a Cyber 175). Switching to a 300 baud link from a VDT to a DEC 10 to submit jobs to the same Cyber 175. Dumb terminals connected to a VAX 8600. Sun Sparc 10 Model 30 Unix (Solaris) workstation. Brief use of a Cray Y MP to run some specialized Fortran code. Stone knives and bearskins. (Can you ID the Star Trek TOS episode?)
OK you beat me! This was because I got my first computer at Secondary school in 1991. My parents wouldn't buy me a computer earlier (1985) because I would play all day and not study! I remember in late '80s some of my friends had Spectrum ZX 128KB with a tape recorder. I was then gathering some Spectrum cassettes to play when I would buy my own computer. When time came, in Christmas 1991 I finally bought a PC! Fortunately the shop gave me a 360KB 5.25" floppy with some games to play and then I had some of my friends. Before my first computer I had a pod clone (the Atari game with the two vertical lines playing tennis and other games) which I connected to the TV, but that doesn't count. A friend of mine remembers having computers with punch cards at school...
Younger posters probably read these and think now I must be an old geek, well not that old! I'm not even 40 yet.