Hard drive defragmentation is not difficult, and there is software available for this task for any operating system. Windows includes as part of the operating system "Disk Defragmenter" (in Accessories/System Tools); there are also free third-party tools available like Auslogics Disk Defrag, MyDefrag, and Defraggler. The Macintosh operating system has basic defragmentation routines which run automatically, but should you wish you can purchase Disc Warrier or iDefrag.
If you want to do your own harddrive recovery, you will need proper software to do it. Go online and download harddrive recovery software and try that. Hopefully, it will not need to be replaced.
No it is a software program
Perfect disk, they even claim that it supports SSDs.
Defragment the hard drive.
No. In order to read data that is deleted, the harddrive would have to be removed and special software would be used to retreive it. If you want to check it out, look on the internet for Forsenic Software or undelete software.
A PS3 harddrive is a standard size notebook harddrive and are only worth the amount of a used laptop harddrive of the same GB size. The $50 extra currently being charged for the 320 GB harddrive is about value of a new 160 GB harddrive so a used 120 GB harddrive would be worth much less.
Defrag
Memory, CPU, perhaps virtual memory on the system drive, and temporary space on the hard drive being defragmented. How much of each is needed depends on the software used to do the defragmentation.
There are programs that do the fragmentation faster than does the Windows software. One such program is Diskeeper, which can be set to work automatically, all the time, in the background.
The harddrive is the same but you need to change the software for the new model
Your old PS3 software in your harddrive is different and does not match the slim hardware. It might work enough to allow you to load slim software like you would have to do if it were a blank harddrive used for an upgrade. Your problem is not new. From what I understand that you want to get the Data out of a PS3 which I assume is no longer working, try researching at the Playstation Support Canter. I added a link to start with at replacing and upgrading a harddrive
Harddrive