Depending on the OS you are running, defrag can take a long time.
Might download HD Tune Pro (30 day free eval) and run it against this drive.
On the Health Tab, check to see if there are any problem areas identified.
Then on the Error Scan Tab, run a Full Error Scan to see if there are errors on the Disk.
Lastly, on the Benchmark Tab, run a Benchmark scan to see that it is performing properly.
You could also download and run Piriform's Defraggler, which will defragment the HDD by a different algorithm.
I have found over time, that defraging by a different program, (Symantic Utilities, Defraggler, PerfectDisk), then the builtin Windows Defrag runs smoother and faster.