At first I bought into the same kind of thinking with paper - why use paper, when I can haul around documents on my laptop? After all, my laptop weighs the same whether the hard drive is empty or full. And surely I was saving the environment by not cutting down all those trees, right?
Now I'm not so sure.
The reason? A recent UN report that found that 1.8 tons of raw material is required in the manufacture of the average computer. Looking at the report, they only consider the impact for the purpose of obtaining the music - but what about playing the music back? What about social pattern differences that result once people start using computers? For example: how many people just leave their computers on all the time now? Wouldn't it be better to have a CD sitting on the shelf (ie: not consuming power) than having a computer running all the time, awaiting the moment a user decides to play back their digital files?
The report text itself points out that the material intensity data is of low quality, so I think this report has to be taken with a grain of salt. While the activity of getting music itself might be proven to be more "environmental", the larger impact of computers, built from highly toxic and difficult to separate materials can not be discounted.