I have my friends iPhone 2G which has been recently upgraded accidently. I think he was on firmware 1.1.3. I dont know the unlock mechanism use on his iPhone originally.

I am trying to look up for the iphone version using the key codes but it doesnt show up the page where the firmware version and other information is available.

Since he is not a techie he doesnt even know which version of firmware he has used to upgrade from iPhone.

Also, I have a windows PC and wanted to know what are my options to unlock and jailbreak the phone ?

if it was upgraded to 3.1.2 use blackrain

Once you have jailbroken, you can check if the unlock needs to be reapplied, use boot neuter to do this but be careful to set the auto lock for your iPhone to never first and do not restart the iPhone once you have started boot neuter running, let boot neuter finish first even if it is taking a long time.