I have an old western digital my book 250gb essential edition external hard drive and it stopped working for awhile and just left it there.

I have some time to try to work on it now.

So... one day my computer wasn't able to detect my hd. The light is on and I hear the disk spinning, but my computer won't detect it. It's plug and play so there are no drivers.

Can anyone tell me what's wrong and how I can fix this?

Does the computer indicate a new USB device has been found when you plug it in?

It indicates it.. but it gives me an error message.. it says unrecognized usb something something.. it went away too fast couldn't get the whole message.

Just as a test have you tried both front and rear USB ports?

Yup I tried both ports. (front and back)
But sometimes when I plug it in it doesn't give any error messages or anything and it doesn't show up in my computer.

Now I'm noticing something new when I plug it onto the back. An windows error message pops up

Windows - Device Timeout
The specified I/O operation on \evice\Harddisk3\DR14 was not completed before the time-out period expired.

Do you have another computer you can try it on?

This would tell you if the drive is a problem or if it is the computer.

Tried it on my brothers computer also.. gave me an unrecognized device also.

That error indicates a drive failure.

You might try the WD Diagnostic:

WD Support > Downloads > My Book

What is the exact model you have?

wd2500i032-001