First you will need some files:
Cygwin, PS3 Keys from PS3Tools Key Pack or Attachment 574 (or another source), and fail0verflow_ps3tools_win32.rar
Run the Cygwin setup and install with all default options and packages.
(We'll assume you installed to C:\)
Once Cygwin is installed its time to set up our key files. For this tutorial we'll be using the ps3.rar file linked above which contains 3.50 keys for games such as Gran Turismo 5 Need For Speed Hot Pursuit and others. If you'd like to extract other games or sony files you will need to find the appropriate keys in the PS3 Tools Keypack or elsewhere.
Extract ps3.rar into C:\cygwin\home\(User)\ Where (User) will be your windows username, and already be premade for you by cygwin.
You should now have a .ps3 folder (IMPORTANT: please note there is a period before ps3) containing 3.50 keys in C:\cygwin\home\(User)\
Place your EBOOT.BIN (or SELF) that you wish to decrypt into C:\cygwin\home\(User)\
Navigate to C:\cygwin\bin\ and extract fail0verflow_ps3tools_win32.rar into this folder.
Navigate to C:\cygwin\ and run Cygwin.bat
In the window that pops up, type unself EBOOT.BIN EBOOT.ELF and press enter
Navigate to C:\cygwin\home\(User)\ and collect your newly decrypted EBOOT.ELF file!
That's it folks, its not as complicated as many of you may think. With this guide, anyone should be capable of decrypting their own EBOOT.BIN's and SELF files. Now, the ELF file that is created is not runnable on the PS3 yet. However, this tutorial is only for walking you through the decryption process.