iPhone up to latest jailbroken firmware (guide up to 2.1)
Alright, what I've got here is the easy mode that works for me and it always has. If it doesn't work for you then go search somewhere else for help?
- Load up iTunes 8.0
- Backup your iPhone
- Shift+Click on the "restore" button on your iTunes' iPhone screen
- Find the file that is linked below (link incoming)