I was having a problem on a machine I was setting up yesterday. I was doing the usual Windows Update on a new install of XP, but it kept displaying an error message for Microsoft .NET Framework 3.0: x86 (KB928416).

I did a few things, including stopping the IIS, but this failed, until I stumbled upon this site.

Basically, you need to download Microsoft .NET Framework 3.0 Redistributable Package. Once you have done this, do a Windows Update again and everything should be wonderful.