Check which versions of the .Net Framework are installed
Installation path
%systemroot%\Microsoft.NET\Framework
Versions of the .NET Framework
The released versions of the .NET Framework have the following version information. .NET Framework version Revision
3.5 Original release 3.5.21022.8
3.5 Service Pack 1 3.5.30729.1
3.0 Original release 3.0.4506.30
3.0 Service Pack 1 3.0.4506.648
3.0 Service Pack 2 3.0.4506.2152
2.0 Original release 2.0.50727.42
2.0 Service Pack 1 2.0.50727.1433
2.0 Service Pack 2 2.0.50727.3053
1.1 Original release 1.1.4322.573
1.1 Service Pack 1 1.1.4322.2032
1.1 Service Pack 1 (Windows Server 2003 32-bit version*) 1.1.4322.2300
1.0 Original release 1.0.3705.0
1.0 Service Pack 1 1.0.3705.209
1.0 Service Pack 2 1.0.3705.288
1.0 Service Pack 3 1.0.3705.6018
*The Microsoft .NET Framework 1.1 is included with the 32-bit version of Windows Server 2003.
Source : http://msdn.microsoft.com/en-us/kb/kb00318785.aspx