Ok, now I see why you did it the long way using all :: for hotkeys.
Basically I went back to the source in your download and just added the
IfWinActive bit. The other wrinkle is holding the Left Mouse Button down while
hitting a key. That way I can use the mouse click to make the desktop or some
non application space active, such as task tray. While holding the left mouse
button down I just hit a letter key. Otherwise I have to click someplace to make
a safe window the active window, then let go of the mouse and hit a key combo.
If you are more keyboard oriented this is probably no hassle as you may hit
AltTab to go to another window or some other key combo. But I'm mouse
oriented. This is just a variation more comfortable for me. I hope you don't
mind me tromping on your ahk code. It's just a handy util so I wanted to
modify for the mouse oriented types like myself.

edit: even with the hotkeys all hard coded using :: the calls to EmptyWorkingSet()
keep memory usage in the tray under a MB.
;DriveKeysAtoZ.ahk
;Opens Explorer to the root of the desired drive letter.
;Version 1.0
;April 23, 2007
;Author: A. Russo (app103)
;Home page: http://www.appsapps.info
;Email: apps.freeware.apps@gmail.com
;Visit DonationCoder.com for more great original software.
;NOTE:
;The hotkey combination I used will not work on 9x systems.
;I will change it or compile a 9x version as soon as I can think of
; an appropriate key to use in place of the Right Control key.
; limitations on active window and change of RCtrl modifier to
; left mouse button by MilesAhead
SetTitleMatchMode,RegEx
GroupAdd,DesktopGroup, ahk_class CabinetWClass
GroupAdd,DesktopGroup, ahk_class ExploreWClass
GroupAdd,DesktopGroup, ahk_class Progman
GroupAdd,DesktopGroup, ahk_class WorkerW
GroupAdd,DesktopGroup, ahk_class Tray
Hotkey, IfWinActive, ahk_Group DesktopGroup
~LButton & a::
IfNotExist, A:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore A:\
_EmptyWorkingSet()
return
~LButton & b::
IfNotExist, B:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore B:\
_EmptyWorkingSet()
return
~LButton & c::
IfNotExist, C:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore C:\
_EmptyWorkingSet()
return
~LButton & d::
IfNotExist, D:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore D:\
_EmptyWorkingSet()
return
~LButton & e::
IfNotExist, E:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore E:\
_EmptyWorkingSet()
return
~LButton & f::
IfNotExist, F:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore F:\
_EmptyWorkingSet()
return
~LButton & g::
IfNotExist, G:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore G:\
_EmptyWorkingSet()
return
~LButton & h::
IfNotExist, H:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore H:\
_EmptyWorkingSet()
return
~LButton & i::
IfNotExist, I:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore I:\
_EmptyWorkingSet()
return
~LButton & j::
IfNotExist, J:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore J:\
_EmptyWorkingSet()
return
~LButton & k::
IfNotExist, K:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore K:\
_EmptyWorkingSet()
return
~LButton & l::
IfNotExist, L:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore L:\
_EmptyWorkingSet()
return
~LButton & m::
IfNotExist, M:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore M:\
_EmptyWorkingSet()
return
~LButton & n::
IfNotExist, N:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore N:\
_EmptyWorkingSet()
return
~LButton & o::
IfNotExist, O:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore O:\
_EmptyWorkingSet()
return
~LButton & p::
IfNotExist, P:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore P:\
_EmptyWorkingSet()
return
~LButton & q::
IfNotExist, Q:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore Q:\
_EmptyWorkingSet()
return
~LButton & r::
IfNotExist, R:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore R:\
_EmptyWorkingSet()
return
~LButton & s::
IfNotExist, S:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore S:\
_EmptyWorkingSet()
return
~LButton & t::
IfNotExist, T:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore T:\
_EmptyWorkingSet()
return
~LButton & u::
IfNotExist, U:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore U:\
_EmptyWorkingSet()
return
~LButton & v::
IfNotExist, V:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore V:\
_EmptyWorkingSet()
return
~LButton & w::
IfNotExist, W:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore W:\
_EmptyWorkingSet()
return
~LButton & x::
IfNotExist, X:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore X:\
_EmptyWorkingSet()
return
~LButton & y::
IfNotExist, Y:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore Y:\
_EmptyWorkingSet()
return
~LButton & z::
IfNotExist, Z:\
MsgBox, 4112, DriveKeysAtoZ, Drive not found, 2
else
Run,explore Z:\
_EmptyWorkingSet()
return
_EmptyWorkingSet()
{
Return DllCall("psapi.dll\EmptyWorkingSet", "UInt", -1)
}