On 1st Jan 2013, the program guide suddenly stopped working. It claimed it had downloaded the guide, but every program had "No data available" on it.
After some research on the 'Net, I discovered that the UK TV guide was downloaded from Broadcasting Data Services, and that Microsoft's agreement with them appeared to expire on 31 December 2012!
I spent a whole day investigating what to do about this. Microsoft were no help at all. I considered upgrading to Windows 8, but the Microsoft free offer of a Media Centre registration key via email doesn't work (at least, I had no reply to the request I sent a week ago).
The only obvious solution I found on the net was to use a separate program to extract the guide information from the broadcast EPG, and put it into Media Centre. To that end, I installed a program called EPG Collector from SourceForge, installed it, and got it working. Except that it couldn't put the data into Media Centre, with the error message "Could not load file or assembly 'mcepg, Version=184.108.40.206, Culture=neutral, PublicKeyToken=31bf3856ad364e35'".
Further research, and a posting to the relevant forum, suggested I install something called the Microsoft TV Pack, an upgrade to Media Centre - this does not seem to be available from Microsoft, but I found it at http://digiex.net/guides-reviews/guides-tutorials/media-guides/699-windows-media-center-tv-pack-2008-download-installation-guide.html. I downloaded it, and the PlayReady PC Runtime (also from Microsoft, and linked from the same page), and installed them both.
I restarted the PC, and Media Centre - all my TV settings had gone! (This is normal, I think, as TV Pack is a major upgrade.) I went into the option to set up TV, and it appeared to hang at the point where it should have downloaded the guide. I panicked, and did some more research - others had the same problem, but none of their solutions seemed to work. So I started it again, and left it overnight.
In the morning, success! It had probably abandoned the download, and continued - it had scanned the available TV channels, and I was able to proceed (after another delay while it tried to download guide information again).
I then laboriously went through all the channels (some of which had got guide information from somewhere, and some hadn't). I pressed the "i" button while the cursor was on a channel name in the guide, and chose "Edit Channel" (this is a new option, which only appears after you have installed TV Pack). This gave me the option to renumber the channel (for some reason Al Jazeera had joined BBC2 on channel 2!), and to set up listings for the channel. In most cases, there was an option to "Use listings from broadcaster" - which I assume gets the listings from the broadcast signal, just as a Freeview TV would. There were a few obscure channels where this was not an option, but I left those alone (I wasn't interested in any of them, and most had too weak a signal to actually get a picture).
I now have a full guide, and I am hoping I will not need to use EPG Collector after all. I have lost all my series recording settings, but they were about due for a clear out anyway.