This is the drive which is called the Seagate FreeAgent Go, I am going to disassemble now(It is available in 500GB and above I think) . You end up searching for the screws!, There are no screws on the external enclosure. The enclosure is composed of two pieces stuck to one another using a adhesive.
Now pick a razor and slide it into the front groove. The top cover is made of metal. Dont put too much pressure on it to pull it, as it might bend it permanently. Just pull it a couple of mm and slice the razor through the front and sides only. Don't slice it through the back as it might damage any wires running for the glower. You are basically cutting the adhesive, and you neednot worry how to put it back. The adhesive sticks back, once you are done with ur work.
You need to be very careful from now, as the wires and connections are becoming more exposed to your tools.
See the metal enclosure and the LED glower which is a white strip on the left. Do not pluck out carelessly, but with care. The metal enclosre has screws on its side which can be removed with a medium star screwdriver. The disk can be thus removed from its enclosures.
Once you remove the screws and take the disk out. This is what it appears to be. 
The otherside of the disk looks like this, with a PCB attached with 7 screws. If you want to see what went wrong with the disk, you need not remove this pcb from the disk. I unnecessarily opened this. However you can take a look at what is inside.
If you remove the PCB. this is what it looks like. Nothing important here to do. Now lets invert it and open up the metal casing again. 6 screws
If you are opening six screws, the metal piece still doesnt come out. That is just because there is one more hidden screw inside the label. Under the top right where "500GB" is written.Without peeling the label carelessly, use a razor to open the label and unscrew the screw inside.
Open the metal case and you find the disk inside. Ensure that there is no dust around and you have ample light to see through as all components are miniature. Keep some very soft tissue papers for cleaning any finger prints anywhere. You can see the Platters and read-write head here. 
I removed an orange "supportive grove", which is not visible here. However ou can see one of my read write is damaged with a hanging head down(tiny ant like thing hanging at the bottomg of the head). 
See how small the head is w.r.t my index finger.It is not possible to repair the head with bare hands and normal eyes :). Need a microscope and micro foreceps etc. I hope you can find your errored components and fix them. Good luck
