I've kerpplonked an updated beta build of HLSW (admin tool for Half life type games) that should be compatible with left for dead in the following place:

http://sneakymonkeys.com/l4d/hlsw_1_3_0_6b_setup.exe

You can use this to admin the L4D servers (although they don't usually require adminning)

I'll get the admin accounts stuff setup soon and post back when its done.