Unable to enable disk use on iPod

I'm using iPod Video, one of the first batches. I only switched recently from PC to Mac and even though the reformatting works and the music switch seamlessly between the computer, I'm unable to enable disk use for my iPod now.

I know where the checkbox is because I enabled it on my PC before, but on my Mac the checkbox is greyed out. Please help if you have gone through the same problems? If not I'll bring it in to the store...

Oh wait, rephrase. Is there a way to both enable disk use and manually manage songs and playlists? I vaguely remember having both checked without one of them greyed out. Or am I just being dumb?

I should be able to view the files in my iPod on PCs as well right?

You can't manage songs manually. itunes works well though...