dangermouse

Hi, this is a bit random and probably not related to anything on this board but I just have to know, cos it's driving me mad. I have the Sony MZ- N510 MD Walkman, which can put stuff into groups for ease of finding music. When I put the shuffle mode on to randomise the order of music, sometimes it randomises the whole disc rather then just the tracks in each particular album. Does anyone know how you can turn this on or off, as sometimes I would rather it did the whole disc and sometimes just the groups. I have managed it on a few occassions but can't seem to get it working again. Any help would be much appeciated.