In Nautilus, they are all mountable, but not in Thunar and PCManFM.
How to make all partitions detected by Thunar/PCManFM? Actually, it's possible to use nautilus, but i'm currently using Xubuntu (i don't want nautilus replace xfce-desktop). Or, how to add them to /etc/fstab and /etc/mtab, so they can be used with "mount"?
In PCManFM, only NTFS partition is mountable (by clicking directly on the icon), but it didn't work on FAT partitions.
In Thunar, no drive is displayed at all, except removable disks.