So, having failed miserably to find a version of Quake 3 which existed where it was said to be, and contained all the files they were supposed to contain, I changed tack a bit in my learning about the Raspberry Pi. The media centre that is the most commonly available for R-Pi seems to be XBMC, and there are a few flavours and options around. I chose to use another SD card and down load and install a copy of RASPBMC, a variation on Raspbian that is tailored and optimised for XBMC.
So I used the Windows installer provided, which downloaded automatically onto the SD card, then booted the R-Pi using the new SD card, which then proceeded to download and configure the whole system. It politely suggested that I went and got a cuppa, which I did, and when I got back, it was sitting waiting for me, booted and waiting to go. I had a couple of issues with my KVM switch and my wireless mouse and keyboard, but rebooting with everything switched and connected seemed to make it all work.
Within minutes again, I was playing AVI movies directly off my external had drive, with audio and everything. Clicking around a few options, the photo library software looks quite nice, the Weather application automatically recognised I was in Wellington NZ and worked fine. There are some issues with media types and codecs I need to work through, but so far most impressive! I suppose I should look at a DTV card for TV reception, and see whether I can listen to BBC radio 4 extra over the internet. If I can do all that, it can replace my Acer media centre PC downstairs!