OK folks, I'm now really confused.
I've been up most of the night and used most of this morning trying to work out what I did to get MCE working. I've messed about with some stuff and now...I've gotten it working again with my ProSavageDDR! And I've not got a clue what it was that got it working! Argh!
OK...here's what I've done so far this morning which has resulted in MCE working. I imagine that it could be a combination of everything that has worked.
Firstly, the version of driver that I currently have installed for the ProSavageDDR is (according to the system properties) 6.14.10.25. (Sorry - I know that the version numbers when you download the driver are different, but I'm not sure what this one is - I'm pretty sure that it is the most up-to-date one that Windows update downloads and installs.)
The videocard is set to display at 1024x768 and 16-bit colour.
As I mentioned earlier, I had added the registry settings to allow a card with less that 48MB RAM to run MCE. I went in today and DELETED those, along with the other entries in HKLM/Software/Microsoft/CurrentVersion/ Media Center/Display Settings. There were some entries relating to resolution and colour depth.
I also ran dxdiag again and disable the DirectDram acceleration setting.
Then I tried to run MCE and was given a message saying that my videocard was not supported...but then MCE ran anyway!
I'm confused through lack of sleep and food! Knowing my luck, it'll probably stop working later on!
Hope this helps some people!