Installing files according Win version

According to Win version I need to install different files.

I think to do it like this:
98 => Call some function
2000 => Call some other function

Better ideas?

You could have two directories, one containing 98 files, the other containing 2k files... then just change what the current directory is based on the OS. Of course this will only work if you are copying files into a single target location but it's just an idea :P