Apple Iphone Jailbreak upgrade help

[boombox]

Can you help me please:

I have a 3GS iphone on 3.1.3

it's a new boot (MC) and the firmware is 05.12.01.

I have jailbroken it before and have Cydia, but I'd like to upgrade it to 4.0 or 4.1 (UNTETHERED) i don't want 4.2 as it's tethered and that is not a good thing for a phone!

PLUS i don't have an IPSW (Crucial) i looked in the folder and there's nothing there. What should i do? do i find an IPSW? If i get someone else's IPSW will it ruin my iphone?

Please help, i'd like to get to 4.0 or 4.1. safely.

Please don't link me to Devteam, i've been there, there is FAR too much to sift through. I tried.

A little Tut would be nice

Thankyou

 

[chyyran]

Go to this link to get an IPSW. It won't ruin your iPhone, but it will erase everything on it as it is a clean IPSW straight from apple. Transfer your music and purchases first using iTunes.

http://theiphonewiki.com/wiki/index.php?title=Firmware


Then, follow this guide
http://gbatemp.net/t243897-complete-ios-jailbreak-guide to jailbreak.

After, read this to install frash and SSH.
http://gbatemp.net/t254055-the-ultimate-gbatemp-idevice-guide

Also, install SBsettings, it's useful.

http://gbatemp.net/t243897-complete-ios-jailbreak-guide

 

[Chaz.]

You may need to have your SHSH saved to upgrade as we are now on 4.2.1.

Apple always push devices on lower firmware to the latest and stop allowing lower firmwares to be upgraded to. I.E- 3.1.3>4.2.1 not 3.1.3>4.1>4.2.1. It makes the big jump if you don't have your SHSH saved in cydia or TinyUmbrella.