My Transcend external hard drive has been working perfectly fine until I plugged it into my laptop last night and it did not appear in my computer or seem to be recognised at all. It didn't show up when plugged into my xbox like it usually does, and did not show when I checked on my pc today.
 - It still lights up when plugged in though.
Any help?

Please keep in mind that I'm clueless with computers so the simpler the BETTER please Hi

Are you using the cable supplied with the harddrive ? some cables are to long and cause the drive not to get enough voltage to start.
Can you hear the drive spinning?

If  the above checks OK then open windows disk management and see if there is a Transcend drive shown maybe it has just lost it's drive letter.

Here is how to use disk manager in windows 7    http://pcsupport.about.com/od/windows7/ht/disk-management-windows-7.htm

Hey,
I've been using the cable it came with and it has always worked fine so I don't think that's the issue.

I opened the disk manager and the drive doesn't show in there at all :/

Just plugged the drive in and noticed it is making a kind of beeping NOISE at first when plugged in, and then NOTHING?It may be gone beyond repair. It might be the power supply of that external unit has failed.   Most consumer device sold  now have little  or no repair options.

IMHO, you should consider getting a new unit. EXPECT to pay about $70 for a good 500GB band name. from Amazon or Newegg. Save the warranty information.*censored*. Well thanks anyway (:Hi

That drive is in 2 parts there is a usb to sata converter board and then a 500 gb Samsung hard drive. The noise you are hearing could be the drive not starting. If you need to get the data off the drive it WOULD be worth removing the drive from the case and attaching it direct to a computer. Doing this will make returning under warrantee impossible so that data would need to be important.