I want to install PowerShell2.0 on a Win2k3 system. I was told to go download and install .NET Framework 2.0. Stupid me figured that .NET Framework 4.0 would work fine. (It's two better, innit?) Turns out it's not.

I'm still uninstalling 4.0 and installing 2.0 (and getting stuck with the ununinstallable "Windows Imaging Component" that 4.0 required), but what the hell is with all the .NET versions?

ISTR that 2.0 obsoleted 1.1, but it seems that if I want it all installed (and why I would want that I don't know), I have to install versions 2.0. 3.5 and 4.0.

What I'm looking for is how they're different, why I would want one as opposed to another (other than specific software prerequisites), and how they manage to be completely distinct from each other.

Update: I finally finished installing 2.0, and now I have to install SP2. It's unclear if I needed to install 2.0 first, or if it's incorporated in the SP2 installation.