Does WIN 7 support dotnet framework ver 3.51, 3.5. 2.0

yes

.Net 3.5 SP1 is already installed, it's the standard for W7. However, if you're developing or using any softwares that uses version 3.5, you have to make sure they are compatible with W7 ^_^

Well I have 2 applications run on dotnet 3.5, whenever I run these applications it asks me to install .net framework. It's anyway to install .net 3.5 on Win7? As I said I've  downloaded from internet, but can't install it. When I execute exe file nothing happen.

Might be wise to check your current framework version.

- Open My Computer and navigate to C:\Windows\Microsoft.NET\Framework folder (If the folder cannot be found, you do not have any version of DotNet installed)

- If you have more than one version of DotNet installed you will see multiple directories.

- Open any of the folders under Framework, then locate the Mscorlib.dll file.

- Right click on the file and select Properties.

- Click the Version tab, and then note the file version.

Let us know ^_^

Yes I have V1 to V4 under framework folder. But I can't find the file Mscorlib.dll in any folder under framework.
In this case Win7 has included all .net version, why when I install an application a error message appears no .net and ask me to install it.

I found Mscorlib.dll in version 2 file version 2.0.50727.4952 and in version 4 file version 4.0.30319.1.

maybe you need .NET 1.1
That version isn't covered by 3.5, but .NET 2 is.

No it doesn't work.

Use the .net cleanup tool and go from there.  Too many outdated versions on your computer. You may only need the most current version.

http://www.aboutonlinetips.com/repair-remove-and-uninstall-net-framework/

I go back to the application vendor to fix up their application with .net. I have .net frame work every version  in Win7, but their application couldn't recognise it.
Thanks for your help guys.