How to restore iPhone 3G iOS 4.2.1 BB 6.15

[hollowlognz]

I've jailbroken and unlocked my 3G on 4.2.1 with BB updated to 6.15.
I believe I have to use custom firmware to restore, but I'm not sure what to do; I'm using windows so I can't make it myself.
Can anyone post a step-by-step of how I can restore? I'm having major battery drainage issues so bought an AT&T sim in the hopes activating it officially will help (as opposed to jailbreaking which I did when I got it to activate it).

Thanks in advance

Additional info: I have SHSH saved for 4.0, 4.0.1, 4.0.2, 4.1 and 4.2.1

 

[maturola]

I've jailbroken and unlocked my 3G on 4.2.1 with BB updated to 6.15.
I believe I have to use custom firmware to restore, but I'm not sure what to do; I'm using windows so I can't make it myself.
Can anyone post a step-by-step of how I can restore? I'm having major battery drainage issues so bought an AT&T sim in the hopes activating it officially will help (as opposed to jailbreaking which I did when I got it to activate it).

Thanks in advance

Additional info: I have SHSH saved for 4.0, 4.0.1, 4.0.2, 4.1 and 4.2.1

Try this Website, http://www.iclarified.com/

You will find step by steps for everything you want to do.