It's called X-Mouse and most people set it on or off with a tweaking program. Do you have tweakui.
Mouse Settings
This tip specifies whether to use a X-Mouse style interface. An X-Mouse interface (in part) means that windows the mouse is over are active. This has been added to Explorer Options on the Explorer page.
The user preference mask is a hexadecimal representation of bit values. To set use Windows Calculator and the values from the table below.
To use Windows Calculator take the value from UserPreferences and AND it with the value from the table below.
a.. Put the value from the table below into Calculator in Hex mode
b.. Press AND
c.. Take the value from from user preferences (in this sample 000000fd as it's byte order reversed).
d.. If it is set it will return the same value as the table below, if it's not set it will return 0
Action Value in Hex
Turn on x-mouse 1
If on bring window to top 40
REGEDIT4
[HKEY_CURRENT_USER\Control Panel\Desktop]
"UserPreferencemask"=hex:fd,00,00,00
;Sets the amount of time the mouse has to be over a window to activate it.
;In milliseconds in byte order reversed (00000bb8 = 3000 ms or 3 seconds).
;Default is 0 seconds and the key does not appear by default.
"ActiveWndTrkTimeout"=hex:b8,0b,00,00
