The drive is not that old. I got it for Christmas. It worked properly before. I had some files saved in it, that I wished to transfer to the WinXP computer. Then I realized that XP can't read exFAT, so I wanted to reformat it to NTFS.
But now, even that computer with Vista keeps saying that it's not formatted when I click on that drive under "My Computer". (Obviously, I moved those files out beforehand lol.) Meanwhile, when I tried using the XP computer to re-format it, the drop down menus, that ask which kind of file system and allocation unit size, in the format function show up blank; and the "Start" button is grayed out.
I think I will try downloading the disk tools, as you've suggested. (Uh... Where can I download it?)