(error 20)messege shows in itunes...plz help

[ahmed08001]

hi guys..m heaving 2G iphone n i wre using firmware 2.2.1 but whn i tried to update to 3.0 ..finally my iphone blocked...whn i try to downgrad firmware 3.0 to 2.2.1 in itunes shows (there is a unknown error 20) guys plz help how can i resolve this prob...i m using windows vista n 8.2ver of itunes ..i also tried wth quickpwn app but it was unsuseful also....
thnx alot 4 ur attention....hoping very soon 4 ur reply

[Moi un Mouton]

Follow this vid to get the phone into DFU mode: http://www.youtube.com/watch?v=ofpinyGlQ8I

Connect it to iTunes, use option restore to get to the stock 3.0 firmware file. You can get that here if you need to:
http://www.iclarified.com/entry/index.php?enid=750

Use RedSn0w again.

Restore from backup after running RedSn0w.

Hope that works for you.