Totally screwed up display in IE7

I have a (atleast i thought so) completed website which in FF and IE6 looks like this:
http://www.kirupa.com/forum/attachment.php?attachmentid=41109&stc=1&d=1171154356
but in IE7…well look for yourselves:
http://www.kirupa.com/forum/attachment.php?attachmentid=41110&stc=1&d=1171154400

Looks like the problem is the background image which is being scaled to suit different resolutions but i dont know how to fix it in IE7!
Here’s the actual link:
http://bine.homeftp.net/kemont

Please help!

P.S. I used more or less this tutorial for the background:
http://www.alistapart.com/articles/supereasyblendys