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I don't think so, but you can do a Self-Cert, which is pretty simple, easy and free, instead of applying for a real Certification. Its great for around the office use.
Also, I don't know if it is true in earlier version of Access, but in Access 2007 you can set up "Trusted Zones", which basically says to trust any Access database that is run from a specific drive mapping (for example, automatically trust any Access databases stored in C:\MyDatabases\). So it isn't always necessary to sign the database to have it be trusted.