The comments I've seen in other places say you must have the previous
versions installed or 4.0 won't install and/or run.
Tim Munro said:
If .NET 4.0 is a completely new framework, will anything compiled for 1.0
up to 3.5 work with only 4.0 installed?
The only mention that I see of previous versions in the readme for .Net
4.0 have to do with an error installing .Net 1.0 after .Net 4.0. If you
need 1.0 for some reason, it is suggest it be installed first.
Here is the link to the readme with the system requirements.
http://download.microsoft.com/download/B/5/7/B57D25A2-B3FD-4668-91B9-DB43B6BD910D/NETFx4RTM.htm