I recently cloned to a larger hard drive, and everything's been going okay, but more recently I'm getting random slowdowns that I didn't get with my old hard drive. I'll hear the HDD working hard during those moments, and the activity light goes crazy. My computer is effectively frozen for a few seconds, and then it's okay. Also opening Explorer seems to take a lot longer than before (just a white window appears for a few seconds before the folders and files populate), but both HDDs are single-platters spinning at the same speed. Feels slower than a 5400RPM drive a lot of the time.

My question is, the old drive was a 320GB Seagate Barracuda (circa 2009) that came with my Dell - 7200RPM, SATA 2, 512byte sectors. The new drive is a 750GB Hitachi Deskstar - 7200RPM, SATA 3, 4K sectors. Both were used in a SATA 2 port. When I cloned to the new drive, would I be getting worse performance because the 512byte sectors were copied to a drive that uses 4K sectors?