Is a positive on an expired test still a BFP?

I just took an HPT and got a BFP, but after I took it I realized the test expired in July. I am planning to run to the store first thing in the AM to get another HPT, but in the meantime I am trying to figure out if I should be excited or not! Is a BFP on an expired test (07/2010) really a BFP? Or is it most likely a false BFP???