Can you provide more details?
Are you typing the web address exactly as it is uploaded on your hosting acount, i.e. If your domain is "www.webassist.com" and you uploaded the PG folder (PowerGallery100) then the address should be "www.webassist.com/PowerGallery100" in order to start the installation process. Need to keep all capital letters cap and all lower case letters lower case for the install to run. Hope this helps.