[How To] Downgrade iPhone 3G from iOS 4.0.1 to 4.0

Here are the steps to downgrade iOS 4.0.1 to 4.0 (tested working on iPhone 3G)

1. Download iOS 4.0 firmware.
   
   
2. Download BlackRa1n and run.
   
   
3. Click the "make it ra1n" button. For those having problems with missing ASL.sll, you have to run the program from these folders:
   
   32 Bit Windows – C:\Program Files\Common Files\Apple\Apple Application Support
   
   64 Bit Windows – C:\Program Files (x86)\Common Files\Apple\Apple Application Support
   
   
4. Connect to iTunes, hold down shift key while clicking "restore", select the 4.0 firmware.
   
   
5. Wait, you're done!