I use guest session to let others use my computer without opening my personal data on my drives, it was working okay on ubuntu 9.04 till one day when I open the guest session I see my drives mounted on the desktop and allowed to be opened , I tried to make unprivileged user the same problem accure

Is there a way to make the guest session works like before ?

Does Ubuntu use PolicyKit? If so look at "polkit-auth --user guest". There are a couple policies about mounting drives. One for fixed partitions, and the other for removable media. There is also a gnome tool for managing policies: polkit-gnome-authorization

Also what are the permissions of your home directory. Look at "ls -ld /home/*". What is your default group?
What are the permissions of "other". If you have a partition with your personal data that isn't in /home, you could mount it inside your home directory. Remember that even if the mount point isn't visiable on the desktop, they can still enter it and read files if the permissions allow it.

I didnt know how to use what you said :S, thanks for trying to help me
any other suggestions

I am not clear what drives you are talking about that the guest can see. If you are concerned about the guest seeing the files in your home directory, you can change permissions on your home directory to prevent that. The guest may still see icons on his desktop, but he won't be able to access your home directory. This would be a good idea anyway, because as jschiwal pointed out, the guest doesn't need icons to be able to access your home directory if permissions allow it (unless the guest account is in a chroot jail).

You can restrict permissions on your home directory from the command line with:

To do it with a GUI, open up your file manager, click the up arrow in the tool bar and right click the folder for your account. Select properties and go to the tab that says permissions. Under "folder access" for both "group" and "other" select "none".

Either of these methods will prevent the guest from accessing your home directory regardless of absence/presence of icons. I can't help you with the other things jschiwal talked about since I don't have a current enough installation of Ubuntu. But you can probably find out what he meant by doing an Internet search on the terms he used.

Could you indicate which drives. What filesystem did you use when you formatted their partitions, and where they are mounted? Are they external or internal drives? If they don't contain system directories, you can: mount them inside your home directory so they can't reach the mount points, and change the ownership & permissions so you have exclusive access.

It they are external drives, using the UUID or LABEL of the filesystem instead of the device with user option, you can restrict access to them. For FAT32 & NTFS filesystem, also use the "uid", "gid" and "user" mount options. Then "your" system will always mount them with the same ownership & permissions, giving you exclusive access on your system.