When there is problem starting your PC, sometimes Windows
automatically enters ‘safe mode’. This causes Windows to use default settings:
VGA monitor, no network, Microsoft mouse driver, and the minimum number device
drivers required to start Windows.
Why would you want to start your PC in safe mode?
If you've ever tried to defragment your hard disk and it can’t complete, it is probably because another program keeps accessing the disk. When this happens, an error message is displayed that says 'Some other program has interrupted the defragment process and defragment is restarting'. This process continues in an endless loop and the defragment process never completes.
Using safe mode usually allows Defrag to complete.
1) Shut down your PC
2) Restart your PC and hold down the F5 key. Don’t release it until you get to the screen in step three.
3) Your display will show a screen where you have a number of choices. Choose safe mode, which should be selection #3.
4) Your PC will start and your desktop will appear very different. This is normal for safe mode.
5) Run defragment as you normally would. If you need details on defragmentin.
6) When defragment has finished, restart your PC normally.