Here is some classic drag and drop code that should help you.
Looks like you were missing some parenthesis and you should maybe get rid of that forward slash before the instance name of computer...
Code:
on (press) {
//Start Dragging Movieclip Behavior
startDrag(this);
//End Behavior
}
on (release) {
//Stop Dragging Movieclip Behavior
stopDrag();
//End Behavior
if (eval(this._droptarget) == _root.computer) {
_root.gotoAndStop("red");
}
}
PS - keep in mind that this code (with the _root. part) is trying to send the main timeline to a frame label of "red" (not a frame label within a movie clip). If you want to affect the timeline of a movie clip (like coin_mc), you would add that like this:
_root.coin_mc.gotoAndStop("red");