[ThrowawayB7]

And what would you do with the Windows 2000 source? It's 32 bit x86 code and the driver model for Windows has changed significantly since those days so it wouldn't run on modern x86-64 hardware anyway. Maybe it would run in a VM but I wouldn't care to bet on it.

[userbinator]

Port it to 64-bit, obviously; the NT kernel has already been ported to a few non-x86 architectures.

[spijdar]

Making Windows NT 64-bit is very different from porting it to a 64-bit CPU. Case in point, the NT 4 (and Win2K) releases for the Alpha CPU were technically 64-bit (so far as the CPU lacked a "32-bit mode") but were functionally 32-bit, with all pointers truncated to 32-bits.

Further case in point -- the AXP64 port (64-bit Alpha) of NT didn't have the ability to run 32-bit Alpha software. If you want that, you have to develop WoW64. So in this hypothetical "port Win2k to 64-bit processors", you would need to create WoW64 from scratch. Alternatively, rebuild a lot of software which is old enough to run on Win2k but also aware of 64-bits.

Or take the AXP approach and literally treat AMD64 as a strange 32-bit CPU, not unlike the x32 port for Linux. At that point you have no binary ABI compatibility with any Windows port, and will need a custom compiler port, and compile all executables from scratch.

[unleaded]

thank god the 2003 source leaked too!