You might need to shutdown WL and reboot before running WD. I have had WL not release the comport properly. You can only have 1 program communicating with the serial port at a time. If you want to run more than one weather program then you need Virtual Vantage Pro. Currently I am running WD, WL, VWS, Aprs, and Cumulus on a Windows 7 box (Dell Optiplex 960) and the computer hardly runs hard at all.