Idk in the WiFi card in the E1705, but in atheros cards that's a driver's configurable parameter.
If you are confortable manually editing the registry go to the key:
Expand that key and browse through the entries (0000, 0001 and so on) until you find the key that contains the WiFi adapter settings.
Expand that key and look in the subkeys for a parameter that reminds you of LEDs (in the atheros drivers these parameters are "ActivityLedFunc" and "LinkLedFunc").
Alternatively open the driver (the .sys file) of the WiFi card with a dissasembler and look for text strings. Usually this way you can find which configurable parameters the driver admits. See if any of the parameters reminds you to LED activity.
Sorry I can't provide any straightforward solution, but I don't even know which WiFi card the 1705 comes with.
Edit: OK, I had a ramage, and the setting that controls the behaviour of the LED in the Intel cards (2200/2950/3950) is "LedEnable".
How the values given to that parameter affect the LED's behaviour is something I can't test, but an educated guess is if you delete the parameter the LED will stay on while the MiniPCI card is hard/soft enabled and off if the card is hard/soft disabled.
If you give it a value of "0" (null) it will allways stay on. Different values than "null" and "0x10001"/"0x1" will have different effects (if it blinks due to general activity, link ready, link up, frequency of the blink etc. etc.).
This guess derives from two observations:
-The way the Atheros card driver behaves:
Different values affect the frequency of the blink. From a "patterned" blink that I guess means "Link Up" to a more random blink that looks like "Activity".
-The way my old Intel 2200BG card used to behave.
In the driver .inf (used the latest available, 220.127.116.11), that setting is only applied for ABG cards and not BG cards. (If you open the w29n51.inf on a text editor and search for "LedEnable" you will find it under "[Reg_Common_ABG]")
This means that this setting never applied to my 2200, and this is the way the LED used to behave:
Off during POST and OS boot (if the Mini-PCI that you are using is in the Dell BIOS "whitelist" so to speak the system will keep it hardware disabled until the OS boots up completely to save battery).
Solid "On" upon login screen.
Solid "On" during operation.
Off upon hard/soft off.