How to preserve baseband or upgrade without losing current baseband help plz??

[Phenith]

I have an iPhone that is on baseband 4.26 but only running iOS 3.0

How do I upgrade without losing this precious baseband?

I'm not worried about jumping right to 4.2.1, if there is a lower iOS that I can install without it updating my baseband I would gladly do that.

 

[kiwijase]

Jailbreak 4.2.1 - 4.3 - 4.1 Unlock - Jailbreak iPhone 4, 3gs, 3g, ipod, ipad

 

[Phenith]

Jailbreak 4.2.1 - 4.3 - 4.1 Unlock - Jailbreak iPhone 4, 3gs, 3g, ipod, ipad

I'm not a mac user so pwngtool is no good for me, would i be able to do it with tinyumbrella?

All the guides for tinyumbrella I have seen say it's for iphone 4 only.