Hi,
I have heard many opinions on defragmenter software - which one is best?
Thank you.

What have you heard?

I never found any need to use any other than the built in one from Windows.

I am also satisfied with the built-in Windows one although I have, in the past, used Diskeeper Lite, which seems to be the most popular third-party defragmenter. That seems to work better if you have very low free disk space when you try to run the defragmentation process.