I had a iPhone 3GS with no SIM card, and so I jail broke it last summer. I have not gotten around to using it a lot, so it's been sitting in a drawer for a few months.
When I turned it on today, it said I could update to a new OS. Because it is jailbroken, when up you update the iOS, it is unbroken....I forgot this until after I had started the iOS update to 6. However when the iPhone connected to install the new OS, it went into a reboot cycle. The apple could come up, stay on that screen for a few seconds and then reboot. After doing some research it seems that Apple does not support the firmware for iPhone 3GS and that this is a common problem.
To fix this the only solution seemed to be to download and run the latest version of redsn0w for win. Later I came across another possible method using a program called evasi0n.
Running redsn0w allowed me to get it back to iOS 5.1.1.
I wanted to see if I could get it to iOS6 somehow, but could not get it to work. redsn0w supposedly has an tethered jailbreaking method, but I could not get it to work....will try again later.
The reason I wanted to get this old 3GS working again is that I wanted an iOS device in case I needed to try out some things for work/education. With my using a Kindle Fire HD, I won't have another iOS device to test item on. With a jailbroken device I can still get apps from the iTunes store to test out.
I have the following devices: Windows 7 Dell Laptop, Kindle Fire HD, Motorola Droid Razr and now an iPhone3GS.