One problem is that Microsoft have always been obsessive about maintaining backwards compatibility. As the owner of a Mac Mini that can't run Mountain Lion (10.8), only Lion (10.7) and a MacBook Pro still stuck on Snow Leopard (10.6), I'm no fan of Apple's enthusiasm for disowning even fairly recent and capable hardware (the Mini actually has the same CPU as the other which can run Mountain Lion, it just has a lesser graphics card - completely irrelevant in actual use, particularly since the machine is headless anyway!)
At Dundee University, apparently several of the applications we use don't yet work on 64 bit Windows - it doesn't help that Microsoft has changed some key file paths. Even 32 bit Windows 7 doesn't work properly with one application...
Worse still, while 64 bit Windows can still run 32 bit applications, it cannot run 16 bit ones - and a great many Windows applications are still distributed with 16 bit installers! To get around this, Windows has a 'blacklist' of known 16 bit installers and built-in substitutes - a hideous workaround at best.
It doesn't help that Microsoft has never supported the multi-architecture files Apple has taken advantage of right back to the M68k-PowerPC transition: unless you use a pure emulated system like Java or .Net's bytecode (MSIL), you have to choose one architecture (x86, x86-64, Itanium, ARM) and be stuck with it for that whole package. (You can't even have a mix of 32 and 64 bit code in a single MSI installer file cleanly, various bits break then!)
Compatibility, the two-edged sword
At Dundee University, apparently several of the applications we use don't yet work on 64 bit Windows - it doesn't help that Microsoft has changed some key file paths. Even 32 bit Windows 7 doesn't work properly with one application...
Worse still, while 64 bit Windows can still run 32 bit applications, it cannot run 16 bit ones - and a great many Windows applications are still distributed with 16 bit installers! To get around this, Windows has a 'blacklist' of known 16 bit installers and built-in substitutes - a hideous workaround at best.
It doesn't help that Microsoft has never supported the multi-architecture files Apple has taken advantage of right back to the M68k-PowerPC transition: unless you use a pure emulated system like Java or .Net's bytecode (MSIL), you have to choose one architecture (x86, x86-64, Itanium, ARM) and be stuck with it for that whole package. (You can't even have a mix of 32 and 64 bit code in a single MSI installer file cleanly, various bits break then!)