How to determine whether service packs are installed for your Microsoft .NET Framework installation?

Use MMC 1.2 to determine the version of the .NET Framework that is installed

The .NET Framework Configuration tool, a Microsoft Management Console (MMC) snap-in, exposes the full version number, including service packs of the existing installation of the .NET Framework. This tool is only available on operating systems that have MMC 1.2 and later versions.

If your operating system is Microsoft Windows 98, Microsoft Windows Millennium Edition (Windows Me), or Microsoft Windows NT 4.0, you can download MMC 1.2 from the Microsoft Download Center.

The following file is available for download from the Microsoft Download Center:Download the Immc.exe package now.

For more info check: http://support.microsoft.com/?id=318785