You need to find out the name of that partition (e.g./dev/hda3, or /dev/hdc4 or /dev/sda2 etc)
As root you can type '
' it will list all the drives.
Then edit your /etc/fstab file
Find the entry with the partition you are talking about and modify it. Mine looks as follows:
/dev/sda8 /home/sycamorex/data auto auto,rw,user 0 0
After you've modified fstab, as root type:
you should be able to write to it now.