Mouse pointer

I have a desktop running XP and have a Logitech buetooth mouse. All was good until this am, I was opening and closing files, usingboth the left and right click buttons when somehow - just by seemingly the combination and speed - and possibly the position of the pointer on screen - I've changed the way the pointer behaves vis a vis single/double click. Firsly, I have the task bar set to auto hide, it operated as it should do but now,I have to click once to get itto reveal.unless I click again, when I move the pointer up into the screen, the task bar expands. So I click once more and can move the pointer into the main body of the screen. However, a single click anywhere in here engages what would normally be the click and hold funtion i.e a dotted line that forms a rectangle appears and follows the mouse pointer wherever it goes on screen and if that happens to be across desktop icons etc, it highlights them as normal. The only way to stop this is to double click. Upon opening a folder or something for example in the control panel (I've been trying to rectify this for hours now) again, a single click will highlight the ion like normal but, the icon is also held so, moving the pointer drags the icon with it. Double clicking will open the item as normal, and this can be done using either the left, or right mouse buttons. This is an incredibly frustrating problem,can anyone help please? Cheers