Hi, I sympathise with your problem. Had a hell of a time myself and this Building database schema seems pretty familiar to me.

I got SS to install and tried a number of possibilities I listed here:
http://www.silverstripe.com/site-builders-forum/flat/231038

Essentially, my tips are here:

Check your PHP version - should be 5. If 4, there's the reason for your problems
Check if "allow_url_fopen" is set to on. If off set a php.ini to switch them on
Get a command to tell your server to enable mod_rewrite (see my blog). Make sure it's right for your server / directories.

Go away, do some shopping, have a cup of tea, and wait for your host's server to update everything. Come back and see if it works

I am new to SilverStripe and I am surprise that the core developers has not taken a greater interest in trying resolve this very important problem. The product is only as good as the technical assistance shared within the community.

Caps