This is something that has annoyed me since I changed to Windows 7.
I haven't done double clicking for a long time now since Windows introduced single click activation (Folder Options > Click items as follows > Single click to open an item).
The problem is, when I press CTRL and hover over the items, they get selected/deselected automatically with every small amount of mouse movement I make.
What I want is to select/deselect the items only when I enter/exit them. So to deselect an item I'm hovering, I have to move the mouse off of it, and then back on.
I'm using the official IntelliMouse Explorer drivers.
Here's another related annoyance: when you are hovering over something and move the mouse onto another item (while holding CTRL) the new item may or may not get selected. If you continue moving the mouse it gets selected/deselected as you move.
I have found that the parameter
HKCU\Control Panel\Mouse\MouseHoverHeight /
MouseHoverWidth have some influence here. If it's set to 2, the item select/deselect really quickly as you move the mouse. When set to larger numbers, its slower. But setting to 20 or 200 doesn't seem to make much difference.