You see, originally I could only see the partitions on the external HDD that I had setup on it a while back from my boot manager & partitioning software (BootIt Ng), and not from either XP or Ubuntu (which I have setup in a multiboot on my computer), or Win 7 on another computer. I wished to solve this problem by using Testdisk from Ubuntu, so I booted into Ubuntu, opened up the Terminal, and started up Testdisk. Selected "Create a new log file", selected my USB hard drive, hit Proceed, and on the next screen, selected "Intel/PC partition", and then hit "Analyze" to search for lost partitions. Once it was done (and yes, it did locate the three partitions on there, which previously it wasn't seeing), I figured that probably wouldn't be enough for the OSes to see the partitions, and access their filesystems, so I next exited back to the main menu, and selected the "[MBR Code]" option to write Testdisk MBR code to first sector of the hard drive, which said it completed successfully. So next I rebooted, hoping I would now be able to get into my partitions from my operating systems, but alas...now the problem is much worse!!

Now I cannot even see the hard drive (much less its partitions) in my boot manager/partitioning software with the USB drive connected. I have also tried booting directly from my USB HDD by putting it first in the boot order of the BIOS, but all that happens is, the BIOS skips the external hard drive, and does not chainload it (probably because it can't even see it), and instead loads up my main internal hard drive. And of course, now I can't even see the hard drive from my OSes.

So does anyone have any idea how to solve this problem, which testdisk appears to have caused?? Also note that now my USB hard drive makes a weird clicking noise when I connect it to my computer, and it turns on, almost as if there was some writing operation or something that failed to complete on it, and now it keeps trying to finish it without suceeding...but that's just a guess. So I'm certainly open to any suggestions or thoughts to a solution for the problem.
Thanks in advance.