Why Does My PC Crash? Reason 5 of 7
Fragmented hard drive
Your hard drive can become a bit more fragmented—and unstable—every time you save a file, install a program, or delete something. Not only does this slow down the hard drive, it can also give your OS trouble when trying to find necessary files to function. So your system will eventually give up and try again—with a crash.
Defragmenting your PC is as easy as pushing a button.
Run the Disk Defragmenter in your System Tools every week or so to keep your files straightened out. The process is a pain in the butt while using the PC (you can’t save data to the disk while it defragments), and it can take upwards of an entire day to complete. So set it and forget it before going to bed or work.
One very important note, however: Defragmenting isn’t necessary for solid-state drives. SSDs already store data in a sequential order (as opposed to random order) and can be susceptible to damage if defragmented.