"The famous 'Class not registered'
Typically, you will encounter this error with XP Pro IIS 5.1. As
usual, there's way to solve it, however the root cause of this is
still unknown :)
Anyway, you will get this in event log:
Event Type: Warning
Event Source: W3SVC
Event Category: None
Event ID: 36
The server failed to load application '/LM/W3SVC/1/ROOT. The error was
'Class not registered'.
So, what do you do ? "