Seagate Baracuda 7200.8 300GB Hard Drive

So I am trying to add this hard drive. I use sysinstall, and I get an error of wrong cylinders/heads/sectors so it recommends some for me.

I format it for freebsd, and then I go to the Disklabel Editor, and I tell it where to mount and I get this error when I hit W to write the changes:

mount: /dev/ad4s1d : Operation not permitted

I am doing all of this as root. I try to mount it to any folder and I get the same error. What could I be doing wrong?
Two things: I assume "any folder" means one you know exists, e.g. /mnt or one you made beforehand?
And could you check with mount that it's not already mounted somewhere?
(I know that sounds odd if you constructed it a moment earlier, but ... still.)
Happened to me a few days ago. ;)
(Using sysinstall on a running system is ever so slightly finicky.)