Seriously though,
Because the programs are so different and because people, myself included had multiple freezing when trying to over-ride 4.8 with 5.0, you should UNINSTALL 4.8 from Add/Remove programs in Control Panel, than reboot. Than install version 5.0. After about 1-2 minutes your definitions will auto update. Than go to open the program, Click on Maintenance, fill out the Registration Form (must be on-line to do this) and click submit. You will get a new license key usually within seconds. You're done!
Jack