STOP - don’t freeze HD until you know for sure that it’s dead. Questions need to be asked/answered first.
The first thing to check is the drive jumper - if you connected the drive as a secondary drive, then you must change the jumpers on both primary and secondary drives to be sure they correctly reflect that (or that both jumpers are set to auto-select and the bios, OS, and type of connecting cables support that).
1. Is the HDD (hard disc drive) in question a recent larger drive? The bios of older computers can not recognize HDD larger than 32 gig. And the bios of really old computers freak out if not below 1 gig. The bios is the software hardcoded on a chip on the motherboard that starts the computer, tests basic hardware, and calls up the OS (operating system - Windows, Dos, etc.).
2. If the bios recognizes the HDD, but your OS does not, then the file system type might not be recognized by the OS on that computer.
3. The file system used might be locked (such as NTFS) or encrypted. This is probably not your problem (yet) if you can not even see the drive listed.
4. If you can get a computer to recognize the drive, but just can’t access the files (assuming the same file system), then you might be able to recover the drive with a very good program designed to do that. I use Spinrite 6 by Steve Gibson. It is a very good program which I have used for many years (starting with version 1) and has a reasonable price. It has several levels of recovery which take progressively longer for the deeper levels if needed (up to a day for deepest level and really large drives). It’s very thorough and worth the money. I have recovered some really messed up drives using this program:
5. If your data is really important, there are very good data recovery services/companies that can recover all your data for a fee, even on physically damaged drives.
Hope this helps.
When you moved the drive to another computer did you detach the drive in the receiving computer.
If you just plugged it in along with the other drive you would likely have two drives on the same cable with both set as Master....in which case only one would be recognized....