Despite what I said previously, when I opened my PC to replace the RAM inside, I found two 512MB sticks rather than a single 1GB stick. This meant that I only needed to discard the faulty module and could keep the good one. Added to the newly-purchased replacement RAM, I have three 512MB sticks now: a very smooth 1.5GB altogether.
And a new DVD-writer too. Well, I was opening the box, so I might as well … 🙂 At least this meant that I could do that backup I’ve been meaning to do for ages ….