I purchased a WD Caviar Black 640GB 7200RPM SATA 3.0b/s 3.5" internal hard bare drive. I'm building a new computer and would like to know if I can just copy my current hard drive to the new bare drive, then upgrade to Windows 7? Would that be the less problematic way?
You're probably better off installing Windows 7 fresh on the new drive - that will eliminate left-over and fragmented files from your old installation. Once the installation is complete you can copy the files you want from your old drive to the new one.
That method also avoids "burning bridges" which might prevent you from going to your old system if you have any problems with the new one.