I just finished putting together my first build. I thought a good way to make sure everything is running well would be to try some benchmarks. I'm new to this, but I downloaded and ran PCMark05. When opening, it warned me that I needed Windows Media Encoder 9, but even after installing it, and restarting, I still get this warning. Upon completion, it tells me that some of the test failed, but not which ones or why (at least I can't find that info). My results are listed as "N/A".
I would download 3DMark Vantage over 3DMark 05. 3DMark 05 is an older program and may have compatability issues with Windows 7 (guessing this is your OS since it is new). Run Vantage and see what your outcome is.