How do I update my iPhone 3G to ios 4.0.1, iTunes 4.0.2, but not as I want?

I just got a 3G iPhone with OS 3.0.1 and I want upgrade to 4.0.1 ios so I can jailbreak it. The problem is that iTunes wants me to download ios 4.0.2 but I can not do that or else I will not be able to jailbreak -. I tried downloading the ipsw restore the file from another website and update my iPhone via iTunes and it seems that everything works until I get the error 3194 -. Error 3194 after I heard you are supposed to open something in the host called notepad and change it but it says apple does not give me permssion to save after I do. How can I update it?? Please, this is very important.

Talent.

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