Iphone 3G JB went wrong, need help!

Hi, I´m new here and I hope I´m writing in the right Place

Please excuse my english, I hope you understand my Problem.

The Problem is, that something went wrong during the JB and my iPhone 3G was on BB 06.15.00 but still on FW 4.0.1.

Then I tried to update again to 4.2.1, iTunes did it, but in the middle of the update Process it told me that an update to an older Firmware is not possible.

I know that it is because of the BB update.

What I need to get my iPhone to work again is a custom 4.2.1 ipsw with 06.15.00 BB but I´m a Windows User and I don´t know anyone with a Mac.

That´s why I´m asking if somone please could make a custom ios 4.2.1 with BB 06.15.00?

It would be realy great!!!

Thanks!!

Wich Tutorial do you mean exactly?

I can only find Tutorials for jailbreaking an iPhone.

My Problem is, that I´m already at BB 06.15.00 and my iPhone doesn´t accept any Stock FW!

Now I have the "Connect to iTunes" Icon on my Display but I´m stuck there because of the already mentioned reason

That´s why I need a Custom FW.

It would be realy great if someone could upload a custom FW 4.2.1 with BB 06.15.00 and another one (4.2.1) without BB update.

Thanks!!!!!