How to check the Windows-Version?

Hello,

i have another problem with my installer that i made with nsis.
How can i get if the system where i want to install my installer ist a windows 7 or a windows xp - pc?
I'd like to set a variable in order of the system-type.

winver.nsh. It's shipped with NSIS.

perfect, that's what i need.

thanks a lot