Windows NT vs Win Server 2003/2008 for web hosting

my web hoster uses windows nt as server + IIS 6 I'm hosting an asp.net 3.5 web site and it... works great ! So my question is : why buying a win server 2003/2008 hosting instead an "o开发者_运维问答ld" NT if NT works great ?

What you mean Windows NT. Windows NT is not a concrete OS it is family of OS which already includes mentioned by you Windows 2003 and Windows 2008 also. And concerning IIS : if you will choose windows 2003 you will get IIS 6 and IIS 7 if you will choose windows 2008. So what to choose depends on your needs.