Double Click won't work

1. Your mouse is faulty: try another.
2. Check mouse settings in Control Panel to check time interval between clicks.
3. Any desktop icon can be opened by right-clicking on the icon, and selecting "Open" from the menu which appears. I actually usethis method by default as it saves mucking about.

The fact that it works after a few attempts may indicate a grubby mouse ball or gunked-up rollers. If your maouse is one of the standard 'ball' type, turn iy over and remove the ball. You need QTip cotton buds and methylated spirit (don't use anything else). Look inside the mouse interior and you'll see 3 rollers, possibly one white and 2 black. If these appear to have a 'stripe' running round the middle of them, that's gunk (an accumulation of hand/desk grease and debris) and it needs to be cleaned off. My experience is that a gentle thunb nail is the best method to loosen the gunk, then clean with a cotton bud dipped in meths. apply to all 3 rollers. Also apply meths to a clean soft cloth and clean the ball or wash it in detergent. Put it all back together and you should have a result. If it still doesn't work try to borrow a mouse and see if you still have the problem. This way you can at least eliminate 'mouse mechanism' as a cause of the problem.
Best luck