IIS 6.0 Authentication stopped working

Today a (virtual) machine of mine would not authenticate to an ASPX page. I would only get error 403.1 Finally found that Windows server 2003 Service pack 1 changes the integrated authentication formerly called NTLM in favor of Kerberos. I changed the joined of this new VM to a new domain based on Active Directory without created a clean build of the machine and got these strange problems. Finally found a hack to my problem in an article on Technet "Forcing NTLM Authentication (IIS 6.0)".

Note that editing the metabase in notepad to make the setting didn't work the first time. Not sure if this was because I had left the file open or entered it wrongly, or a restart was required (recall reading that a restart is not necessary).

This blog is a personal record of lessons learned - for when they happen again. I think only problems like this one that were not solved within a few google searches will get logged. Lets see...