Open up regedit.exe through the start menu search or run box, and then browse down to the following key: Unfortunately Tweak UI doesn’t work in Windows Vista, so you’ll have to make the registry setting manually, or use the downloadable registry hack file I’ve provided, which will set the drag size to 20 pixels. You can test the effect by dragging the test icon around. Somewhere between 10-20 should help stop the accidental copying, but you might need to set it higher. I wouldn’t set the value too high, because then it will make it difficult to drag things the way you normally would.