A: No! The C:\Windows\Installer folder is used by the OS and should never be changed directly.
If you want to remove applications, use the Control Panel Programs and Features to uninstall them. It is also possible to run Disk Cleanup (cleanmgr.exe) in elevated mode to help free up space.
Read FAQs about Windows, virtualization, systems management and more at John Savill's FAQs for Windows.