Halo 3 Co-Op

I want to play halo 3’s campaign, but it says I need a hard drive. I went and got a sandisk, but that didn’t work :confused: I’m not going to spend 100$ to get another hard drive for my 4gb xbox, and I don’t want to know that I wasted 20$ for nothing. How do I play Halo 3’s campaign without dishing out more money?

Hmm…
You can delete some applications in your xbox 360 to make room for halo 3.
If you spent microsoft points for it, you can delete it and redownload it again without paying more money.

I got a 8gb sandisk, and my halo 3 CD only takes up 5.6gb. So unless I installed it incorrectly… I don’t know.
I have two other sandisks, one for halo 4’s second cd, and the other for DLC’s.
Just to make sure I’m clear: The third sandisk ONLY has Halo 3 downloaded onto it, with some room to spare. My 4gb xbox only read’s two at a time, so I take out my Halo 4 sandisk for 3. I know which sandisk is which, I marked each one so I wouldn’t get confused. Also, I have a physical copy of Halo 3.
It’s really ticking my nerves. Reach, ODST and 4 all have co-op online, so why not 3 as well? Hmmm IDK, they had plenty of time for an update…