installing php 4.3.8 onto windows server 2003 with IIS 6 & multiple websites nightmare

I have various small html websites on my windows server 2003 pc, these
function quite happily from directories under D:\websites via ports 81,
8081, 8091, 8082 and of course there is the dafault web site on port 80.

I have installed MySQL 5.0.0 and php 4.3.8, but i can't get them to work for
another website on port 8090.

If I use the command line and go to c:/php and run php -i, I can see the
test_info file information, including the html.

If I try to run it with http://80.177.100.48/test_info.php I get 'CGI
error - The specified CGI application misbehaved by not returning a complete
set of headers'

When I try to run it via http://80.177.100.48:8090/test_info.php I get a
page not found 404 error.

That pc's name is 'webserver', and is connected to the internet via an
internal ADSL card and networked to my main pc called 'whatever'.

On 'whatever' I have a test installation of phpBB2 set up on
http://80.177.100.48:9999/phpBB2/ which works fine and is quite happily
routed via port 9999 through 'webserver' to the 'whatever' root directory
under windows XP pro.

When installing and testing is finished I would like to have this running on
the 'webserver' pc.

Can anyone tell me what I'm doing wrong please?

N. B.

I forgot to mention that although I am using DNS and WINS, I'm not currently
using 'Domain Controller/Active Directory' on 2003 as it makes things very
slow with only a 128 mb, 1300 Mhz P4 - though I suppose I could, if
necessary.