[Discuss] permissions on partitions

[David Lee]

Good evening

Yesterday, I formated my hard drive, removed win xp and re-installed 
Linux on the whole drive.

When I set up the partitions, I used swap, /, /home and /data. Another 
drive was put in as hdb and /backup.

Normally, when I had windows, I used /mnt for c, e, and d (other drive).
Should I have used mnt for /data and /backup?
When I go to the /data directory (partition?) to make some directories ( 
photos, music, and videos),
I get an "access denied to /data/photo". I have tried reading and trying 
chmod and chown, but to no avail.
This is using Konqueror. If I su and and use command line, it's fine. 
How do I change permissions on a more permanent basis for all users?

I could re-install and use /mnt/data, but I was hoping to learn why this 
was happening.

Thanks for any help

David