The German Society for Informatic in Medicine, Biometrics and Epidemilogy GMDS recommends to use Linux instead of NT servers in hospitals. They warn, that Windows NT, which is advertised as a secure operating system has security problems. GMDS warns also that system security of NT installations is weakend by application software,which sometimes needs incsecure settings to run.
Some stuff is somewhat better, some stuff is somewhat worse.
On the practical side, there are considerable deficiencies concerning the reliability of the implementation. Numerous conceptional security gaps and implementation errors lput Windows NT on the same level as older UNIX systems.