Vista - Project Server 2007 installation does not start: license problem

To introduce Project Server 2007 in my company I'm setting the third project
pilot.
I have a 80% probability to obtain the product.
I don't want to install and configuring the product a fourth time... So I
have installed the following deployment environment:
2003 server se 64x (full license)
SQL Server 2005 (full license)
Sharepoint Server 2007 64x (trial license)

At this point, when I try to install Project Server 2007 (trial) I get the
following error message: "Setup is unable to proceed due the following
error(s): Microsoft Office Server Trial Edition products may not be installed
on a server with licensed Microsoft Office Server products. Remove existing
Microsoft Office Server products and re-run setup. Correct the issue(s)
listed above and re-run setup."

I need a deployment environment where, at the end of 180 days of trial
version, I can upgrade the license from evaluation to definitive.

Can you help me?

Thanks in advance.