Not understanding this

I use Vista Home Premium 32 bit with Vista Service pack 2

 

I notice in C:\Windows\Microsoft.NET\Framework

 

that I seem to have several folders with different versions

v1.0.3705

v1.1.4322

v2.0.50727

v3.0

v3.5

v4.0.30319

 

So not sure why I keep getting updates for v3.5?

 

Shouldn't my new version be 4.0 given I have a folder 4.0.30319?