I had installed MSE when the pc was clean.
I beg to differ on having to format and reinstall.
The pc I mentioned above was F'd up from two worms, a boot sector virus and other malware. The worm deleted a registry entry and a file and broke the TCP stack. Took me 3 days, but it's all clean, with the registry entry entered by hand and a reinstall of SP3 (XP).
It's back in service. We'll just have to see what happens.