Changing Post Order

Hello,

I have created a two column post layout on my site by placing . As is stands now my site displays the same posts side by side (did so by adding two postformat.php in the content div).
11
22
33
..
..

Like I said, the same post are displaying side by side- which I do not want. I'd like it to display posts as such:
12
34
56
..
..

Any ideas?

Thanks,
Eugene.