The left button switch on your mouse is probably failing - try swapping the mouse out before you do anything else.
If this doesn't solve the problem, also try swapping your keyboard to ensure you don't have a stuck key that is interacting with the mouse driver to cause this effect.
In terms of software settings, there isn't a lot that could cause this. In Windows Explorer, go to Tools and Folder Options. On the General tab, make sure the "Click items as follows" option is set to "Double-click to open an item (single-click to select)".
To ensure Windows doesn't have a buggy driver for your mouse, I'd download and install the specific mouse driver software from the mouse manufacturer (i.e. Microsoft, Logitech, etc) - install it, then reset the driver to defaults to ensure that your left mouse button hasn't been reprogrammed. You may also want to play around with the left click speed settings to ensure that they haven't been set to the wrong settings.