since you did not give the
exact path? I have to ask:
when you unzip wordpress (for a manual install) - you get a folder titled
'wordpress' .... now did you upload THAT folder to the root of your domain OR the
contents of the folder?
I have seen quite a few people upload the folder and not just the files in it!
it would make the install path:
yourdomain.xxx/
wordpress/wp-admin/install.php
which would give you an error as the wp-admin folder is 1 level deeper than it should be.
if this is the case? just set it up so that the files
in the 'wordpress' folder (and not the folder) are at the root, and you should be fine
R-