Ok, i will help you.
Try your external drive in place of your (but take care to switch it to DS0 !!!!!!!!!)
After that you'll be able to know if you need to repair your motherboard or the drive !
1st of all get a electrical contact cleaner spray at a local store (WD40 is not so good !!!).
Spread some on the 'disc presence' switch, the HD 'mode disc switch', by the whole on the motor wheel
Turn the wheel, press the switches many times ans re-spread some on them.
Look the long displacement head's screw.
Take off all HARD SOLID AS ROCK dead grease !!!
With just one finger make this screw turn to move the head at least 3 complete cycle and take off all dead grease.
Turn you drive vertically
Spread some contact cleaner on the motor screw, and make at least a complete cycle, then do it again.
Now time to try !
You may have to move again the long screw displacing head at least 3 times (yes there is still on dead grease on it).
9 times out of 10 it's sufficient for me.
:rtfm:
