^^^ Heh...that's never stopped them in the past. Back in 2000 they had:
- Windows Millennium Edition (AKA Windows ME)
- Windows 2000 (Probably the best of these)
- Windows XP (Granted, 1 year later in 2001, but definitely a close overlap)
Then there was Windows 95, followed by 98, NT and - Microsoft Bob all at around the same time (Did anyone ever see this abortion, MS Bob? I did - eewwww!)
Parallel OS development & deployment has always been a "hallmark" of the Microsoft business model, as were/are bug minefields.