Hacking the new installer

I am currently hacking the new installer for PPJoy, moving from the old InstallerVise to the Nullsoft installer. At the same time I am busy converting the installer plug-ins to the new NSIS format. Getting stuff to compile is quick and easy (or it should be!) . Understanding the environment in which the is running is something entirely different... I don't want the installer to be unstable!

Which brings me to the next point... how much effort do you put into backwards compatibility? The method for installing/configuring a Control Panel is different between Win98, Win2K, XP and Vista... there are unique settings for each one of the. Win98, in particular (surprise?), is very different from the NT family.

It is very tempting to drop Windows 98... How many of these systems are still out there?