Visual Studio 2005 SP1 is getting pushed out via Microsoft Update and the one question which keeps popping up here at the office is why the installation fails. Typically this is caused because some version of Web Application Project is installed. WAP is included in SP1 which is why the install fails.
You will need to remove it before you can successfully install SP1. It would appear that the SP1 installation isn't very clear on this.
Just a little heads up. Scott Guthrie posted about this a while back.
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