Hey guys, I have an Iphone 2G and would like to upgrade to FW 3.1.2

I am only using Windows, but i've read in the first page that blackrain does not support jailbreak/unlock and i shoudln't upgrade the baseband.

so what steps should i do? ctrl+shift to restore to FW 3.1.2, then use blackrain straightaway? but how to prevent from upgrading baseband? i hope to get a detailed explanation.

thank you in advance