use filesend2_plus, configure your comport appropriately (this should correspond with your comport settings on control panel/systems/device manager, i always use 9600 BAUD rate). click on open code data, then select your file (dreamsoft). turn on your receiver, hit send (or you can turn on your receiver beforehand and put it on standby mode). you should be able to see the trasmission count on the bottom of the software. @sat6910 is the same as metabox3 and i have the same setup as yours.
are you having any errors, like NAK data, no answer or something to that sort? pls also make sure that you are using null port (you stated this already) and check for the continuity of your cables.