This is the software's you need to jailbreak your iPod Touch 1G/2G and iPhone
and it also includes the software's you need to install "Installer.app."
Use This video to Jailbreak your iPod Touch or iPhone:
How To Jailbreak 3.0 Final iPod Touch 1G, 2G, and iPhone 2G, 3G (Unlocks iPhone 2G) Windows!
Use this video to install "installer 4 onto your iPod Touch or iPhone:
how to install installous (iPhone 3g, iPod touch 1st gen, 2nd gen ect.)
I'm pretty sure that this videos work's. if not you can search by your self on Google or Youtube on something like the title on the videos.
P.S You need a jailbroken iPod before you can install "Installer 4". also known as "Installous". You also need to read the info on right side on Youtube for info and links (if you need any). there should be no problems :)