You may want to try using the  Dell or HP Client Manager to do this for you. You can create a BIOS profile that has the wireless NIC disabled and push it out to the machines in your environment. 

I guess it all depends on if you want the NIC disabled in Windows or in the BIOS.

This script should disable all enabled wireless network adapters on Vista. It will not work on XP.
If you have XP you could perhaps use vbs to enumerate wireless network adapters and disable them using DevCon.

strComputer = "."
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\wmi")
Set colItems = objWMIService.ExecQuery("Select * From MSNdis_80211_Configuration")
For Each objItem in colItems
	strName = objItem.InstanceName
	Set objWMIService2 = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
	Set colAdapters = objWMIService2.ExecQuery _
		("Select * from Win32_NetworkAdapter Where NetEnabled='True' And Name = '" & strName & "'")
	For Each objAdapter in colAdapters
		objAdapter.Disable
	Next
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