Failed to open or save XLS from outlook

If you happened to get this error "Can't open this item. Can't create file: Right-click the folder you want to create the file in, and then click Properties on the shortcut menu to check your permissions to that folder" while trying to open or save XLS, that means you have some issue with how Outlook stores the temporary file.

Use regedit to search for "OutlookSecureTempFolder". Go to that file directory and delete all the files inside. After that, the file can be opened.

The reason for doing is that outlook saves the attachment to the temporary directory first before opening it. Each time you open the attachment the filename stored will be "filename" +"(X)". X will be incremented each time the same file name was saved. The problem begins if you have previously opened the same file name 99 times. The auto filename cannot go beyond the number 99. By deleting all files in the TempFolder, you will reset the number to 1 again. This will allow you to open the attachment without problem.