Remove annoying dashed lines from Excel when printing and previewing

Check your gridlines settings in Page Layout.


How to block specific application (exe) from running in Windows

Use gpedit.msc and use either of these two methods :
To block specified applications :
>> User Conf./Administrative Templates/System/Don’t run specified Windows applications
To run only specified applications (might take a lot of work to populate):
>> User Conf./Administrative Templates/System/Run only specified Windows applications