HDD Defragging

[escoville]

But while we still have hard disks, my recommendation is to keep your system files on a separate partition from your work files. The system partition will hardly ever need defragging, the work partition fairly often, depending on how much you add and delete. If they're both on the same partition, the fragmentation of the work files will slow down the system.
While Defraggler has occasionally defragged things that Windows hasn't, it takes a huge long time.
Apart from Ccleaner (indispensable!), I would also recommend Recuva. But the essence of recovering deleted files is to do it quickly. No one can recover a file that's been completely overwritten. But if you delete something by mistake, Recuva will recover it if you haven't used the computer (much) since the deletion.

[Colin Southern]

But while we still have hard disks, my recommendation is to keep your system files on a separate partition from your work files.

That strategy works for separate disks, but not necessarily so well for different partitions on the same disk as the partitions will reside on different areas of the disk and the heads have to seek further to get to the data (kinda like having to constantly travel between cities rather than just across your existing city).