Hi, If the watch is running it will of course unwind itself. Simply over winding is not a problem, the problem is what damage overwinding has done.
If you have decided the watch is not worth the cost of repair, then get the back off. If you can acheive this without stabbing yourself. You proberbly have the skill to fix the watch. If you get the back off look first for the Balance Wheel. It looks a little like a wagon wheel, with spokes. If you hold the watch upright in your hand and twist your wrist you may see the balance wheel "run" if you can encourage this to keep going for a while, keep twisting. You may resolve the issue. If the B.W will not keep running. Look for a pawl (hook) which engages in the spring's cassette to hold it as its wound. look at where the spindle from the winding button goes. I'm sorry i cant help further its one thing to fix and another to write up.
Good luck
mondsron, January 2008