Hdd problem?

"Could not find the hard drive" is not quite clear enough, so maybe you can provide some answers.
1. What happens as you try to boot up? Normally there will be a series of text messages from the BIOS boot sequence, including notes about what drive units it finds and whether they are working. Does your drive show up OK there?
2. Is this your only drive, the one you boot from? Or, do you boot OK into Windows from another drive, and then find this drive missing in My Computer?
3. If the boot sequence messages indicate the disk is present, when does it NOT find the drive? Does Windows just fail to boot from it? Exactly what is the message?
4. A bad cable or a loose connection of a cable could cause this sort of problem. And yes, many people have had SATA cables vibrate loose from the connector on the unit. Disconnect your computer from power and open the case. Look carefully at the data cable connecting your drive to the mobo port pinout in case you can see a problem. Then, whether you see something wrong or not, simply unplug the cable and plug it back in again, two or three times. Do this at both ends. Then do the same for the power supply connector at the HDD. Close up and reconnect, and boot. If you're lucky this solves your problem.
5. If that does not solve it, try again by replacing the data cable, in case that is the trouble.
6. If that does not work, try plugging the data cable into a different pinout port for SATA. If you do this you should go into the BIOS Setup screens on your first boot and verify that the disk still appears; IF this is supposed to be your boot disk, ensure that the BIOS is set to boot from it in its new port location..

If none of these work you may have a problem with the drive itself. As a first step, using another computer if necessary, go to the website of the manufacturer of your hard drive and find their free diagnostic tools software. You can download it and burn it to a floppy or optical disk. Seagate has Seatools for DOS, WD has Data Lifegard. Run the tests on your hard drive to determine whether it has a hardware flaw. If it does, consult the maker's Tech Support people for how to fix.

If that does not get you a solution, you may have corrupted data on the disk, and that's a different set of troubleshooting. Let us know what you find up to this point.

Yes, the cable itself can be faulty. You can try another cable. As a different test, take your drive and cable(s) and plug tit into another machine to see if it works there. Do NOT try to boot from it - just connect it as an extra data drive on a functioning machine and see if you can use the drive. If it works you know the drive and at least some cables are good and can concentrate on your machine. If the drive won't work anywhere, you know to concentrate on the drive.

Just switch cables from an existing system, that works best as you know that cable must be good because the system you're borrowing it from has run fine for months/years. That way you can rule out probable causes.

Sorry to hear your HDD appears dead. Just as a "last hope" kind of test, see if you can hook it up to another computer and test it with Seatools. If it cannot be found there, too, that confirms your sad situation.