For the following warning in oscommerce installation:
Warning: session_start() [function.session-start]: open(/tmp\sess_5616cfa91211a8ef5ee94d09d21f7eb5, O_RDWR) failed: No such file or directory (2) in C:\wamp\www\catalog\includes\functions\sessions.php on line 67
As a solution they will suggest you to create a tmp folder in your root folder.. You create a folder in your (document) root or in your site root (catalog here) and it would still not work. Hmm. Actually by root they mean it your system root and not the document root or site root. For example, in Windows if your site is located at C:/wamp/www your root is C. So just place an empty tmp folder under C and this warning should disappear. For Linux systems it will be / or /public_html but i haven’t experienced this warning on Linux systems.
I hope it helps someone.