I'd skip the "Buy a cheap bike" step and get a good entry-level mountain bike.
When I decided to give Mountain biking a try, I bought a cheap bike off of Craig's list, it fell apart the first few miles, but the bug had already bitten, so I went to Wal*Mart and bought a better cheap bike (atleast it was new) I soon discovered that although this bike worked, it was so heavy and had crappy components and although it was working, I was working way too hard on that tank. I then visited my local bike shop, test rode a number of bikes, fell in love with a Trek Mamba, the rest is history, I love this bike. There are comparable models, I personally am a Trek fanboy... so in my opinion, you can't go wrong with a Trek, I'm not familiar with the numbered series' (i.e; 4300, 6000, 7000's etc) nor do I know much about the 26", I will only ride 29ers from now on, the Mamba has spoiled me..... look into the Trek Wahoo, Marlin and Mamba for some sweet 29er Hardtail action.
Wahoo - Trek Bicycle
Marlin - Trek Bicycle
Mamba - Trek Bicycle
But you really should get on some bikes at your local shop and find one that fits you and you are comfortable on.