Well to share a folder of Vista or higher with Windows XP you must go to Advanced Sharing Options and Turn off password protected sharing. Also make sure that the shared folder gives full access to Administrators. If this doesn't work you have to also enable full access for Everyone (for certain folders in C, not the whole drive). This is also true for the personal folders (Documents, Pictures etc). Even if you have shared them, you must give full access to open them from XP or you get an Access Denied error. Since you will be giving full access to everyone, be careful which folders you share. Remove access (from security settings) to sensitive folders that you don't want others to see.