A unwanted partition mounted

After bootup I find one of my DOS partitions mounted. Unmounting requires root. As far as I understood Linux, the mounting of partitions is done via de fstab file. Have looked into the fstab and and for both dos partitions the same text can be seen. /dev/hda1 /drdos auto noauto,user 0 0 /dev/hdb2 /drdos_r auto noauto,user 0 0 /dev/hda1 can be mounted as usual, /dev/hdb2 is mounted after rebooting and can not be unmounted from user. Looks like the partition is mounted somewhere before fstab starts or? How can I let /dev/hdb2 behave normal and in accordance with my intentions (fstab)?