I personally never just replace a hard drive in my PC, I usually just add a second hard drive. The Windows performance readings really don't mean much. If you're looking for a reliable form of benchmarking, try [http://www.primatelabs.ca/geekbench/|GeekBench]. My main hard drive is a 1TB 7200RPM Western Digital Greendrive. It only gets a 5.9 in Windows. You won't get much better performance, withour upgrading to something like an SSD.