Untethered iOS 4.2.1 jailbreak is here and availbale for Mac OS X. But the windows has not been released yet. iPhone Dev Team has confirmed that a Windows version of Redsn0w 0.9.7 is on its way for jailbreaking iOS 4.2.1 with iOS 4.1 IPSW instead of iOS 4.2b3 firmware and SHSH blobs.
As per recent Redsn0w_testers (official iPhone Dev team’s account) tweet ,
@redsn0w_testers: Since Apple still serves the 4.1 IPSW (not blobs!), we’ll do a Windows redsn0w release for untethered 4.2.1 via Monte-4.1
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