now... Rather than buying another HDD (or two!) I'm thinking of re-compressing some stuff as xvid or mpeg4. I have a large TV so want to avoid adding new compression artifacts as much as possible. I also want to

I think it is hard to artifacts when recompression occurs. So I was thinking that you might have one more possibility of using "tcrequant" which is the name of the program. It requantizes MPEG stream.

It reads MPEG2 stream and recompresses it by the factor you decide. But it doesn't decode the stream, it increases compression factor from frame backgrounds, and tries to keep the main subject (where the camera focus is) as original.

By this way you could lose about 10% of disk space easily. Of course higher compression ratio is possible but..

Best regards, Jori