iPhone 4 "iPhone says device isn' t eligible for the requested build" Problem

[mrfuzzybear]

Hello, i have an AT&T iPhone, anyways today i jailbroke it on Firmware version 4.2.1 using a program called GreenPoison, i messed around with it for a bit, and tried installing themes and what not, but then i decided that i'd rather go back to the official firmware, when i plugged in my iPhone to my laptop running Windows 7 it wouldn't recognize it, it wouldn't even charge.. So i did something really stupid and i went into my settings and decided to Reset it and erase all content.. Then my phone went into an endless boot, so i decided to put it in dfu mode, which was a success, my windows 7 laptop still would not recognize it, but my iMac running snow leopard did, so i tried restoring it, but i got a "device isn' t eligible for the requested build" error. So now i have no clue what to do..
Is there a way to resolve this or am i just screwed..
All help is appreciated
Thanks Guys!

*Problem Resolved*
I read another thread about using a program called "Tiny Umbrella"
My iPhone is now restoring normally