DV Info Net - MOV Playback in Premiere CS4-Windows

I know there has been some discussion about wrappers and MOV vs MP4 when working in Premiere CS4, but I've got a puzzle that I just can't figure out.

I have a Premiere CS4 system with the Matrox RTX2 for the PC. I have the GY-HM700 (because I also have FCP), and I shoot mostly in the MOV format since it's the most convenient (and I do most of my editing in FCP). At any rate, I wanted to see if I could get the MOV files to work on the CS4 system. I read about the XD Decode software so I installed it, and gave it a shot.

Now here's the strange thing. When I opened the footage on the PC in QuickTime, it played fine and had the gray lines as the watermark (since I had not payed for the software). When I imported the footage into Premiere, there was no watermark and the footage played back fine with no rendering required. I thought this was very strange, so I decided to uninstall the XD Decode software, and the footage STILL played fine in Premiere. I went to a friend who also has Premiere with the RTX2 and sure enough the footage wouldn't play. I installed the XD Decode software and then the footage did play, but had the watermark and needed to be rendered.

I kept thinking there must be a codec installed on my machine that was not on his but I cannot figure out for the life of me what it could be. The only other thing I thought was interesting was that if I looked at the properties for the clips on each system, mine sees the "File Type" as a "Matrox MOV" using an MPEG 2 codec, and his sees it as a "Quicktime".

I have no clue what is going on between the two systems, but I did notice that when I placed the same footage on a new PC system with Premiere CS5, it played back fine no XD Decode required.

Any thoughts from anyone on this? I was hoping to upgrade my system from XP to Windows 7 64bit, but I am hesitant to make any changes for fear of losing whatever is making the system work for me now.

Thanks in advance for any input.