So I bought a monoprice 25ft HDMI to DVI so that I could connect my computer to my TV. I also have a DVI to HDMI adaptor that came with my Bell PVR. Yesterday I plugged my 25ft HDMI to DVI cable into my TV, and connected the DVI to HDMI adaptor to the end of the cable (to make it a HDMI to DVI to DVI to HDMI) and plugged the DVI to HDMI adaptor into the HDMI port on my DVD player...and I get picture AND sound from my DVD player on on my TV. A friend of mine tells me that this isn't possible, but I have no other cables connected to my DVD player and the picture and sound are both transfering to the TV...how is this possible? Am I getting digital sound? Any ideas?

This is quite normal and is possible and was discused just the past couple of days. See the following:

http://www.digitalhome.ca/forum/showthread.php?p=653681#post653681

It's because you have HDMI at both ends. if you used only a cable with DVI at both ends, it wouldn't work.