If you do not own a Mac, I'm sure that you have a friend or a family member who does. That means, you already had the ability to jailbreak the GM build of 4.0 on your iPhone.
Well, if you just didn't feel like finding someone(or didn't Jailbreak 4.0 on an Apple Store computer) your in luck!
Just a few days before the final release of 4.0, the Dev Team and MuscleNerd have finished working on their Windows version of redsn0w.
The redsn0w beta has been updated for 4.0GM on iPhone 3G and iPod touch 2G (non-MC version). Multitasking and homescreen wallpaper are turned on by default (Apple doesn't normally allow this on these 2 devices). You can deselect these features if you choose.
A version for Windows is now provided.
Just like our other betas, this one intentionally doesn't hactivate the iPhone. Please wait for Apple's public release of 4.0 for that part of it.
YOU SHOULD STAY CLEAR OF THIS BETA SOFTWARE IF YOU RELY ON A CARRIER UNLOCK. That's because the beta redsn0w works only if your device has already been upgraded to the stock 4.0beta1/beta4/GM IPSW from Apple, which contains a baseband update. If you installed that IPSW, you've already lost the carrier unlock until the next planned release of ultrasn0w and blacksn0w.
I would say that unless you are really anxious to check out 4.0(and know what you are doing), go ahead. If you have any doubt, just wait until June 21st.
To learn more about redsn0w and for download links click here.