I had the same card (PCI) and the old ISA TV-tuner as well, so I assume that's the components you have as well. I would ask what OS you are using? I have successfully installed that card with its drivers under windows 98SE, but I have no idea about any more recent OS. And I HAVE gotten TV out to work as well.
My suggestions on what to try:
-re-install the drivers for the video card (you don't need to remove them first) and then update your directX. I know this sounds somewhat ludicrous, but slight "tweaks" to my directx config sometimes made all the difference in my being able to run the software correctly.
-remove, then re-install the ATI capture software, and again, update directX. It seems to be REALLY picky about this, so it's always a good idea
-absolute last resort, try booting into "safe mode" and removing ALL drivers for both the main Rage II+ card and the capture board, and then re-boot, and install all from "hopefully" clean. And then again, re-install directx. Beginning to see a trend here?
My install eventually worked, both under Win95OSR2 and Win98SE, but sometimes it would work for no apparent reason, and fail for no apparent reason. You just have to "nurture" it a bit. Praying seemed to help as well.
I hope you get it working
Erioll
PS You DID remember to hook up the proprietary ribbon cable between the ISA tuner and the PCI card right? That is essential for them to work together. If that's not on, it won't work no matter what. If your cards don't have a cable, then disregard my advice. I probably have different hardware. But if they have the PINS for a cable, and your friend forgot to give it to you, get that first.