So broke it can't be fixed

What architectural limitations are in the new version? Is it worth the investment, or will the architecture of Windows 2003 suddenly break when you need a bug fix, but they need the revenue of an upgrade to Windows 2005?

The Register writes about NT 4.0, which is not so old that the architecture should be so different from Windows 2000, XP, or Windows 2003...

In a surprisingly candid admission, the company states that fixing NT4.0 is simply too difficult.

"The architectural limitations of Windows NT 4.0 do not support the changes that would be required to remove this vulnerability," Microsoft says.