Do I need all Microsoft .NET Framework versions?
Solution 1:
There are 4 distinct versions of the .net framework.
- .NET 1
- .NET 1.1
- .NET 2
- .NET 4
All of those can be installed and uninstalled independently. This is where it starts to get interesting! .NET 3 was introduced (along with a service pack to .NET 2) and was an additional set of libraries to it. .NET 3.5 followed this trend (with a second service pack for .NET 2 and a service pack for .NET 3) and again required .NET 2 as it just extended it.
The latest release is entirely standalone and does not require previous versions. It is mostly backwards compatible so it is possible to get your old applications to work on it.
Whether you need any of them or not depends on what you're running. Most applications out there are still built for .NET 2 to 3.5 so installing 3.5 will cover you for that. I would recommend installing 4 as looking forwards that's what Microsoft want people to be using.
.NET 4.5 (and 4.5.1, 4.5.2) is an in-place update to .NET 4.
Solution 2:
.Net Framework 3.5 installation also installs all the previous versions from 2.0 and onward. Version 1.1 is an exception and has to be installed separately.
Since you seem to need the 3.5 SP1 version, this will also install all .Net versions from 2.0 and upwards. So you really have no choice about it, and attempting to uninstall one version may cause problems with the other versions that build upon it.
As there are very few products left that require .Net 1.1, one can wait with its installation until there is a real need for it. As it is not automatically installed, and if it is already installed, this means that it is required by some product that you have installed (unless you are on XP, where it is installed by default).
You have not mentioned .Net 4.0, but with this version Microsoft has tried to reduce the size of the software by not including all the previous versions. .Net 4.0 is therefore smaller, and is supposed to be backward-compatible with all previous versions from 1.1 and onwards. So in theory it is the only one you need.