Andrei,

For me:

BPM = My top 100
Barcode = Videocassette No. (I don't bother with scanning)
Distributor = Minidisc No.
Booklet pages = DVD No.
Quantity = Musical influence rating (how important a track/album is to my music appreciation)
Purchase Location = Place where the music really hit me (Influence location)
Interview (spare tickbox for various purposes)
Private (as above)
Soundtrack (as above)

I know everyone is different, and we're all probably music 'geeks'! Some will always want certain fields - others won't!

Cheers, Malc