can't delete files from external hard drive

Right click on a file - properties and verify who is the owner.
https://help.ubuntu.com/community/FilePermissions

ok so it says the owner is 99 and that I'm not the owner. How did it decide that and is there any way to change it?

You can gain temporarily elevated permissions to administrate, change the owner of the mountpoint of the hd and of the file itself.
Please open a terminal: ctrl+alt+t
Enter:
gksudo nautilus

## Please work with caution since now the complete filemanager is running with elevated permissions.
Navigate to the mountpoint of your external hd, for example
/media/my_external_hd
right click and adjust permissions to your needs; same with the file.

Well that worked in that I can now access the drop down menus to select permissions but it doesn't seem to do anything, even after I click apply. I still can't delete anything.

Can you give the output of:

sudo fdisk -l; mount; lsb_release -a; uname -a

Thanks

Disk /dev/sda: 40.0 GB, 40007761920 bytes
255 heads, 63 sectors/track, 4864 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00029639

   Device Boot Start End Blocks Id System
/dev/sda1 * 1 4682 37603328 83 Linux
/dev/sda2 4682 4864 1464321 5 Extended
/dev/sda5 4682 4864 1464320 82 Linux swap / Solaris
Note: sector size is 4096 (not 512)

Disk /dev/sdc: 119.8 GB, 119832539136 bytes
255 heads, 63 sectors/track, 1821 cylinders
Units = cylinders of 16065 * 4096 = 65802240 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

Disk /dev/sdc doesn't contain a valid partition table
lsb_release-a: command not found
uname-a: command not found

> used to run this hard drive on a mac, is that the problem?
> Disk /dev/sdc doesn't contain a valid partition table

Ah, partition table HFS+ formatted?
https://help.ubuntu.com/community/Fstab#hfs.2B-

>Note: if you want to have access to your files on Ubuntu, you must change the permission of the folders and contained files you want to access by doing in the apple terminal:

sudo chmod -R 755 Folder

When it says apple terminal does that mean this is something I have to do on a mac? Is there a command in Linux I'm supposed to use to bring up the "apple terminal"?

I'd assume it means an 'apple terminal' on a Mac to make them worldreadable first.