A noisy cooling fan - DirecTV DVR

For A noisy cooling fan, relating to DirecTV DVRs and receivers. Love our direct tv tivo (Phillips DSR708). But.....

The constantly-running cooling fan is way too noisy. I can hear it during low audio volumes. I unplug it when we watch DVD movies, (and put up with the 5-8 minute warm-up time when I plug it back in).

It's also plugged into my receiver's power outlet, so the tivo gets powered off during the night, basically to eliminate the constant noise of the cooling fan.

Any ideas? Naturally I don't want to disable the fan, which would disable the warranty! Has anyone come up with some sort of muffler device? :)

Or, is there a retro-fit to install a thermo-device which would only run the fan if the unit overheats? I'd go for that.