The key is independent of the version, provider it is still valid (14 months from issue) it will work, if not. Complete the
avast! 4 Home Registration form and you will receive an email from register @ avast.com (without the spaces) with your registration key.
You can register with the same email, and you will likely to be sent a cpy of your old key if it is still valid (should be from Nov 2007).
Ensure that you uninstall AVG and reboot befor installing the new version of avast.
The new version does support win98se, there are some modules however that won't work due to the limitations of the OS. But, the AV will still berform on win98se.