Microsoft

R2 of Windows 2003 of course. I'm hoping in the Vista craze that this release doesn't get ignored because it has a lot of cool features that you can use without doing application validation all over again because it builds on top of Windows 2003 SP1.

I think it was a good design choice to do it that way. You install Windows 2003 SP1 (essentially) then insert disc 2 and it adds on all the specific R2 features. If you have some sort of application regression that some 3rd party won't support because they've never heard of R2, don't use disc 2 and try it again. If it is repeatable with just disc 1, it's something that would affect Windows 2003 SP1 also.

http://www.microsoft.com/windowsserver2003/r2/default.mspx

You essentially need a fast network card and a slow disk subsystem to ever see this problem but it is definitely worth noting.

http://support.microsoft.com/kb/907404

This explains it better than I can:

This problem occurs because the available memory has been consumed. The available memory can become consumed when the disk subsystem throughput is slower than the network interface. The cache manager should buffer the difference in throughput between the disk subsystem and the network interface. However, hotfix 839406 and security update 896422 bypass the mechanism to throttle back these incoming writes after the data exceeds a certain threshold. If large writes are sustained for a long time, other critical writes will be deferred for a long time. When this occurs, the computer may stop responding.

I haven't tried it myself but with all the backend changes made to SQL 2005, this does not surprise me a bit.
I'd be extra curious to see what it would do on an x64 box.

Seen here:
http://forum.olympiacos.org/blogs/venceremos/archive/2005/10/22/dimitrisv.aspx