How do I disassemble/open a Seagate 1.5TB External Drive STX-DesktopED (B)?

I've just done this myself. You'll need a flathead screwdriver, a phillips screwdriver and a small or precision screwdriver.

You have to be a little bit careful or you'll break some of the tabs or clips.

The shiny top cover is held on to the base by clips. There are four on each side, two on the front, and three at the back. Here is a picture. You can see that I broke a couple of the clips while opening the thing.

http://i181.photobucket.com/albums/x197/haowan/IMG...

I recommend you do the ones on the front first, but I did it with the side ones first, then the back ones, then the front ones last, which was a bit hairy. The hooks are on the bottom half and the clips are on the top cover.

http://i181.photobucket.com/albums/x197/haowan/IMG...

One of the clips at the back is reversed.

http://i181.photobucket.com/albums/x197/haowan/IMG...

To open the clips, use a flathead screwdriver to prise each one of its clip. Don't be shy, keep the drive upright as normal and feed the screwdriver downwards between the top and bottom, then lever it outwards until you hear a click. The click will either be the clip coming off the hook, or the clip breaking. Long as you've got some of the clips left you should be ok to reassemble. Note where the clips are from the pic above and insert your screwdriver accordingly.

Now you've exposed the internal housing, just pop it out of the base by turning the base upside-down. There are now five screws to release - four on the rubber shock absorbers and one holding the metal sleeve in place:

http://i181.photobucket.com/albums/x197/haowan/IMG...

Once you've removed them, take off the LED wire that's taped to the housing and slide out the sleeve:

http://i181.photobucket.com/albums/x197/haowan/IMG...

Now you can remove the hard disk drive by sliding it out from its connector (if you want to remove the mainboard for maintenance there are two screws to undo also):

http://i181.photobucket.com/albums/x197/haowan/IMG...

Good luck! Unfortunately the mainboard on this particular one was not repairable by my amateur soldering skills :(

Seagate 1.5tb External Hard Drive