Cannot install

I'm quite new to this but I am having real trouble installing the network. Can someone help me as I have followed all the install documentation and troubleshooting guide and all I get is an internal server error page.

I just can't figure out what is causing this?!? Any suggestions? Even better yet, does someone just feel like sorting it out for me as this must be like the 20th time I have attempted installing it and failed. I'm getting very frustrated.