After I finished testing out Windows 7 (64-bit) I added the other 4GB's of RAM today I had laying round. I have 4GB's in the system now so this would give me 8GB's total, downloaded Memtest86 and on test 5 it would just start dumping errors like crazy after trying different sticks I said all my ram can't be bad and it turns out it ant found the problem just now after I played Crysis for like two hours with DirectX 10 witch by the way looks amazing. I also ran Windows Memory Diagnostic from Windows and the test came back clean just to be on the safe side.
Quote Doctor Four I think I may be on to something: I tried each of the DIMMs individually in the first slot (A1). Each time I got the same errors at the end of test 5. Then I tried moving the single DIMM to the second slot (A2), and it got through test 5 without any errors. And right now it is running the tests and is up to test #6 and error free. It appears that even though Asus says to use slots A1 and B1 for better overclocking compatibility, the DIMMs are already at their maximum clock speed and don't appear to be able to handle running in slots A1 and B1. The DIMMs are currently in slots A2 and B2. So it appears that if you are not going to overclock the RAM, you would use the black rather than the yellow slots.
Update: After putting the DIMMs in slots A2 and B2 (black slots), it got through the entire Memtest-86 tests without any errors. This bit is not documented anywhere in the manual for the P5Q SE Plus. The only thing the manual says is to install the DIMMs in the yellow slots for better overclocking capability.