Thank you Perry.

I agree with you, I think. It could be better to give full independence to the tempdb from the user database and log files.

And again, thank you for your explanation about creation of additional file groups on the tempdb. During my research I found this http://technet.microsoft.com/en-us/library/cc966545.aspx, which reads as follow: "Only one file group in tempdb is allowed for data and one file group for logs. " Which is the same you explained to me.

Thank you everyone for your comments and help about this.

Hernan.