Hi Antoniovs2008,
I am checking on this error to see what could cause this.In the meantime you can check the installation logs to see if they provide more detail. They can be found in one of the following locations depending on your operating system.
Vista / 2008 : %localappdata%\Microsoft\Web Platform Installer\logs
XP, W2K3: %USERPROFILE%\Local Settings\Application Data\Microsoft\Web Platform Installer\logs
Once in the logs directory open the webPi folder. This contains log files with the summary information from the installations numbered sequentially for each run of WebPi , the highest number being the most recent installation attempt.
In this log there should be details for the failure.
You can post back the log information to the forum or if you prefer you can zip and email the logs directory to webpi@microsoft.com.
Thanks
Richard