making a file system

[Glenn at home]

Thanks to all for all the help so far.
I got brave and decided that I would use fDisk and make another partition on 
my drive.
I made it a primary, and I gave it #2, so I think it is /dev/hda2
Now, I try to mount /dev/hda2 /mnt
and it tells me that I need to specify a file system.
I tried
mkfs /dev/hda2
and the same with /mnt at the end, and in both cases, it says
invalid argument passed to ext 2library while setting up super block
I looked at
man mkfs
but I still don't know how to tell it what file system to use.
Should I put something like X3 or x2?
Thanks