How can I restore my iTouch back to 3.1.2 under these circumstances and after I've tried these methods?

I recently purchased a third generation iPod touch 32GB, and when I got it, it was at version 3.1.2. I jailbroke it, but soon after (I didn’t download any apps after jail breaking – all I had on the ipod relating to the jailbreak was Rock) I accidentally upgraded to 3.1.3. I know there is no jailbreak for that version, so I have tried several times to restore to 3.1.2 by putting the iTouch in DFU mode and Shift+Restoring with no luck because Apple is not permitting downgrades anymore. I’ve also tried tricking iTunes by redirecting servers (this tutorial: http://www.iphone-enthusiast.com/2010/02/oh-noos-i-updated-my-iphone-to-313.html) but that hasn’t worked either (I’m not 100% sure that I altered the host file for that tutorial right, but I’m not sure how to troubleshoot it). What might I be doing wrong? Anything else I can do?

PS – Through this entire processs I have used Windows 7/a PC.