Geoff Chappell - Software Analyst
The IsOS function supports OS_DATACENTER as its dwOS argument in various builds of SHLWAPI versions 5.0 and 5.50 (see below), and then in version 6.0 and higher. However, these two sets of versions appear to address entirely unrelated questions about the operating system.
For those builds of versions 5.0 and 5.50 that support OS_DATACENTER, the function returns TRUE if
For version 6.0, the test is changed to
except that the builds from Windows XP SP2 and SP3 try to have it both ways: these apply the earlier test if the operating system version is 5.0, else the later.
The OS_DATACENTER case of the SHLWAPI function IsOS is available in version 6.0 and higher. An earlier implementation is known in the following builds of versions 5.0 and 5.50:
but is better regarded as a superseded attempt at a different test.
Use of OS_DATACENTER seems rare. One use that Microsoft is known to have found for OS_DATACENTER is in many but not all builds of SHDOCVW.DLL version 6.0, for a feature that may first be seen through an Internet Explorer dialog box:
This feature (or, rather, Microsoft’s particular design of it) requires “Windows Media Player 7 or greater”. If you click Yes but Windows Media Player 7 or greater is not installed, then SHDOCVW will tell you (if your operating system is Windows XP or greater):
This may be primarily a ruse by which one Microsoft application, Internet Explorer, that dominated its market at the time gets to advertise another Microsoft application, Windows Media Player, that had competitors. Anyway, if the operating system is not sufficiently capable or suitable for Windows Media Player 7 or greater, then SHDOCVW does not bother offering the Media Bar, let alone suggesting that you try (pointlessly, as it would turn out) to install Microsoft’s media player.
Necessary (and documented) conditions for the Media Bar are that the operating system be at least Windows 98 or Windows 2000. See, for instance Media Bar is Unavailable on Internet Explorer 6 for Windows NT 4.0. However, there are three ways that an otherwise acceptable system can be ruled unsuitable for Windows Media Player 7 or greater. One is that it satisfies the OS_DATACENTER conditions.
This tie between Internet Explorer and Windows Media Player is withdrawn from SHDOCVW version 6.0 starting with Windows XP SP2. Perhaps it just passed its usefulness or was frowned on by some regulatory authority, but it is curiously contemporaneous with when Microsoft seems to have noticed that OS_DATACENTER is ill-defined, having meant very different things at different times.