I would begin by looking in the BIOS to make sure the computer itself recognizes the drive. If not then it can be a case of a bad IDE or power cable or even motherboard IDE port. It can also be that the drive itself has gone bad.
If it is recognized in the BIOS then I would open Windows Disk Management to see if its listed there but not initialized. It may be listed as a foreign disk and you may be able to import it back into the system.
It may also be a case of it simply needing a drive letter assigned to it so you can view its contents.
Another option is to take the drive out and put it in a USB external drive caddy and attach it to the computer that way or add it as a secondary drive in a different computer and see if you can read it.