Remember in this case redsn0w is being re-used as a quick delivery vehicle for a fix for this Rock.app bug.
Don't confuse this as a "should I use redsn0w or blackra1n to jailbreak?" discussion. This is not the issue we are talking about here.
Not (yet) sure how to hack redsn0w to fix this problem on windows. I have no plans to look at that tonight either. Should be similar/simple to do though.
I dont feel you need to downgrade iTunes as you no longer need to run blackra1n to fix your problem. It is no problem asking about downgrading iTunes as that is completely legal. You can find links to all old versions of iTunes here
iTunes - The iPhone Wiki
It us very important to uninstall iTunes properly and restart before installing another version see this link for instructions.
Removing and reinstalling iTunes, QuickTime, and other software components for Windows Vista or Windows 7
Also your library might be "too new" for the old version of iTunes. there are various ways around this.