Changing rights for mounted partitions in GNOME
 

Hi
I'm using GNOME 2.16 with CentOS 5.1
CentOS mounts my external HDD from Nautilus (with double-clicking), but under read-only. When I goes from 'Computer' to partition options, I can't change from read-only to read & write. And I'm logged under normal user.

How to make my account able to read & write?

You can't without access to mount, which under a normal user account you can't.

If you mean you just want it to be mount from now on as read right to the user then pass the options rw,users,gid=groupid,uid=groupid either in the fstab, or as a mount command with the -o option. The the user and group memebers will have access.