I don't exactly know what to tell you-- it has been a long time since I messed with php & html, but I do remember having similar issues back when I DID mess with that stuff. If I remember, it usually had to do with PHP not being installed or configured properly, therefore Apache did not know how to deal with the php pages and instead treated them as files (to be downloaded), instead of displayable pages..
For what it's worth, you have a lot of broken links on the site. Several things I did notice when I examined the properties of some of the links, is that:
1) Links are comprised of local Windows absolute paths with the C:\ drive as the root.
2) Links have a mixture of forward AND backwards slashes (this might be OK, I'm not sure)
3) If you have webpages whose filenames have spaces in them, change the spaces to underscores or dashes; this can avoid weird problems.
Can you run php_info() locally to verify that it's installed properly?
Also - if I may give some constructive criticism: The water pattern on the index page makes it VERY hard to look at the page. Consider either using a bigger image and/or stretching an image, rather than tiling all those little images
and also, creating higher contrast between the background image and the text.
Sasha