IIS 5.1 and ASP.NET do not work together

Hi, I'm having a very strange problem. When I'm trying to access my simple
HelloWorld type
 ASP.NET 2.0 application, I'm immediately getting the following error:

 The specified procedure could not be found.

 And that's everything that renders on page, it happens with every ASP.NET
application.
 I have WinXP Pro, IIS 5.1, VS 2003 and 2005 Pro, 2.0.50727 Framework. I tried
 aspnet_regiis -i, it completes fine but nothing changes. In IIS manager, I can
 see and modify ASP.NET properties page, it shows everything ok. I also tried
 reinstalling both Framework and IIS.. still the same error. IIS renders simple
 .html documents fine. I have no strange firewalls/security programs installed,
 system is stable. Inetpub folder (and my apllication) both are on FAT
partition,
 so that's not NTFS permission problem. The only thing i discovered is, that I
can't
 register (regsvr32) aspnet_isapi.dll, it says that it couldn't find the entry
point and the
 .dll is only 8KB (perhaps it is corrupted)? I've developed some applications in

 ASP.NET already and I never saw something like that.

 Could someone help me ? I'm slowly losing my sanity here ...

Strange error.

Anything relevant in the System or Application event logs.

No errors/warnings unfortunately ..

Can you copy and paste the exact error message?

This IS the exact error message.