the require once line:
require_once(../../../WA_eCart/Customecart_PHP.php
on a page at:
D:\Hosting\4719347\html\ecartstore\store_static_sp _php\store_static_sp_php\store_php\cart.php
would be looking for the WA_eCart/Customecart_PHP.php file 3 directories below its curant location:
D:\Hosting\4719347\html\ecartstore\WA_eCart/Customecart_PHP.php
make sure the eCart directory is being uploaded to:
D:\Hosting\4719347\html\ecartstore\
For the other error, try deleting the cache file in the users configuration folder. You can find more details in the "Common Installation Issues" pdf file that is linked on the right hand side of the download center:
common_installation_issues.pdf