Don't believe that Microsoft used Windows Server 2003 based OS to build parts of Windows 7? Look in the Windows\inf\Setupapi.offline.log. Only found it by coincidence when I was verifying the job that DISM did when I injected a few drivers... I was quite surprised that Microsoft used Windows Server 2003 to build parts of Windows 7 Professional. I wonder why would they be still using an Operating System they've pushed to phase out, but ironically they use it internally to build the next version of Windows... Here's the evidence I found Code: [Device Install Log] OS Version = 5.2.3790 Service Pack = 2.0 Suite = 0x0112 ProductType = 3 Architecture = x86 [BeginLog] [Boot Session: 2009/07/14 00:06:57.116] >>> [Stage Driver Updates] >>> Section start 2009/07/14 00:47:40.520 os: Version = 5.2.3790, Service Pack = 2.0, Suite = 0x0112, ProductType = 3, Architecture = x86 cmd: C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\AEC17B8A-E8ED-42B1-B8E5-FC036365BD74\dismhost.exe {A34A5EE1-C3AD-4BE4-AB4D-B32EEAD86AD1} sto: Driver Update Context: sto: Image State = Generalized sto: Image Architecture = x86 sto: Transaction = None sto: Driver Updates = 10 sto: Staging all driver updates. sto: {Import Driver Package: D:\work\mount\Professional\Windows\WinSxS\x86_sensorsalsdriver.inf_31bf3856ad364e35_6.1.7600.16385_none_355af82f22f9507d\sensorsalsdriver.inf} 00:47:40.520 sto: Importing driver package into Driver Store: sto: Driver Store = D:\work\mount\Professional\Windows\System32\DriverStore (Offline | 6.1.7600) sto: Driver Package = D:\work\mount\Professional\Windows\WinSxS\x86_sensorsalsdriver.inf_31bf3856ad364e35_6.1.7600.16385_none_355af82f22f9507d\sensorsalsdriver.inf sto: Architecture = x86 sto: Locale Name = neutral sto: Flags = 0x00000245
It doesn't really matter, but it's interesting to see that Windows Server 2003 still lives on inside of Microsoft, at least for now.
Never heard that Server 2003 is "an Operating System they've pushed to phase out". Probably missed something. Anyways, before Windows 7 and may be even now it remains the most stable, fast and effective OS by MS. And what could be alternative to develop Win7 on? Vista? Server 2008? I think - no, cause Win7 has in general the same kernel as they. So they developed Vista on 2003 and just continued the job on the same platform.