B1if Installation Error SAP 9.0 PL04

I experts,

I have this problem: When I try To Installa B1if in the DB server I have this error:

It's in italian, the traslation should be:

"Database Connection Failed: impossible to access with 'sa' user. The user is not associated to any SQL Server trusted connection."

Now, I access the system via termina server using the Administrator credential. I read a SAP note that say the B1if use only trusted connection but this form ask me for a user name and password and I dont understand how to install the B1if this way...

Any suggest?

Thanks in advance,

Jonny Cortonicchi