However, you are strongly recommended to completely uninstall version 4.8 from Add/Remove Programs before you install version 5. Version 5 is so different and improved that the people who have had trouble often times are trying to install over 4.8. Don’t install over 4.8. Remove 4.8 than install Version 5.
After the install, you must register the product. About 30 seconds after Avast updates, open the program, click on Maintenance, fill out the form and register. After clicking submit, your license key is already entered into the program! (No wait for e-mail.) You are protected for 12 months. When that time nears expiration, just repeat the registration process. If you need to reinstall Avast, you must also repeat the registration process.
I installed avast! 5.0 directly over the exisiting 4.8 installation without any problems on two machines. One was XP SP3 and the other Vista 64bit.
The installation ran very (incredible) fast and smoothly.
As i see the installation process, the version 5 installer correctly uninstalls the 4.8 installation during installation. Am I wrong? :-\