Huh,,, difficult question.
I do not think there's whole lotta difference of power consumption between MP3 and WMA. Maybe few percent at most.
Assuming that all your 35gb songs are 160kbps, you need to compress it down more in order to fit them in there.
160x20/35=91kbps. So, if you re-encode them into 96kbps WMA, you will have most of them in there, but not all.
If you want all of them in there, you have to encode them with 64kbps, and this will give you extra space for more music. (64/160x35=14gb, 6gb left)
But remember, the re-encoding will take some time.
(Might as well encode them into better codec...)
(Since I'm a Sony NW-HD3 user, I'm inclided to tell you that Sony's codec sound much better then WMA at 64kbps.
I just bought a Zen Touch (and will receive it shortly). I have about 35gb of music, but the hard drive is only 20gb. It would be nice to be able to fit my whole collection on the player.
I would convert my collection to Ogg, but the player doesn't support it. What I'm wondering is, were I to transfer it as WMA, what would the consequences be?
I know that WMA requires more processing, so I assume I would get less battery life out of the player. I'm wondering at what bitrate of WMA will there be no loss after converting from 160kbps mp3's? 128kbps? 192?
I'm also wondering exactly HOW MUCH less battery life I'll get if I use WMA.