postgresql-8.0.0-beta5-en.msi -- does not install

Dear POSTGRESQL developers,

I would like to test the new PostgreSQL version, but was not
able to start

     postgresql-8.0.0-beta5-en.zip

i.e., the Windows Installer stopped without saying anything.
That happen under Windows 2000 _and_ under Windows XP. The
same happened with older Beta-Versions, I had to go back to

     postgresql-8.0-beta2-dev2.zip

to download a version that installed. But I do not want to
test older versions -- can you help me?

Regards,  Hans Werner Borchers.