Update: iOS4 has launched, and you don’t need to hack anymore to get it! Head here to get the details to get started. Have fun everyone!

Want to get a crack at that iOS4 goodness that Steve Jobs graced us with just yesterday, but don’t have the developer account that you need? We have good news, you can get your hands dirty now thanks to the powers of the internet.

The only problem is this, you need a Mac to pull off what we are about to describe. If you do have a OS X machine, read on. Why the Mac component? iTunes 9.2 is required, and as it stands that iTunes build is Mac only. Sorry Windows users, step aside.

You do not need your UDID to execute the installation, which means that Apple should not (no promises) be able to nail you against the wall for doing what we are about to walk you through.

Guide:

1. To commence, download and install iTunes 9.2 (Mac only, download links here, here, or here).

2. Now you need to download the right gold master for your device and save it on your desktop:

If you have an iPhone 3GS, download this.

If you have an iPhone 3G, this one is for you.

iPod Touch 3G, get yours here.

And finally if you have the iPod Touch 2G, download this.

3. Now let’s actually install iOS4:

Plug in your iOS device, and then tab over to iTunes.

In iTunes, alt+click on the ‘restore’ button, and then when promoted to locate the file select the IPSW file we just moved to your desktop.

Wait for between 10 and 15 minutes for the new OS to be moved over.

All Done. How cool is that?

A few warnings, this is a hack, so if something goes wrong do not come crying to us about it. If Apple gets mad at you, we warned you. Finally, have fun. The real version of iOS4 is scheduled to drop for the public on June 21st, but who wants to wait that long?

A special thanks to GumballTech for doing all the legwork.

Read next: Updated: The UK iPhone 4 Launch: What We Know So Far