Geekshop Install Error

Ive purchased the script about a month ago and wasent able to get any support thru codecanyon on the comment page. When i install the script everything goes smooth up until i get to the point to unzip, During the un-zip process i get a Error 500 time out.., im able to refresh and continue on by skipping thru the previous steps and clicking on Database, i enter the correct database info and it brings me onto the finish page. When i click finish i get this "http://websitename/install//finish"

" Not Found

The requested URL /install//finish was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request. " Someone please help me