arcgis 10.0 - Error post installation ArcSDE for SQL server 2008

I had a problem during post installation of ArcSDE for SQL server 2008, and this is the message :

The ArcSDE Repository was unsecessfully completed. would you like to view this error?

then when I click on OK, what appears is:

Connection to sde failed(0)

please can somebody help me ?

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I am using ArcGIS 10,ArcSDE 10,SQL Server 2008 and for service pack I use SP2