What is Safe mode and Clean boot? How do we use it to troubleshoot?

In Safe mode, we boot the PC with just the essential services and drivers that are required for Windows to run and most of the third party services and all non essential Windows services are disabled. We use this method when we suspect that a third party service is causing the issue or when we are unsure of what is causing the issue. Since all non essential services are disabled when you boot the PC in Safe mode, any issues occurring as a result of these services/drivers will not be present in Safe mode. This way we can identify that the issue is caused by one of the non essential that was disabled in Safe mode.

Once we have determined that the issue is caused by one of the non essential services/driver, we need to determine which specific service/driver is causing the issue. To find out the culprit, we will perform a procedure called as "Clean Boot". In Clean boot we will disable the services group by group until we find the specific service. For example, if we have 25 non essential services, we will disable the first 5 services and boot the computer to check if the issue occurs. If the issue occurs, then the first five services disabled might not be causing the issue. The next time, we disable the next 5 services and boot the PC. If the issue doesn't occur, then one of the 5 services currently disabled might be causing the issue. Then we will disable the the 5 services one by one till we isolate that one service causing the issue.

Steps to boot the PC in Sade mode:

To boot the PC in Safe mode, press Windows key  and the "R" key to gather to get the "Run" command box. Type "msconfig" and press enter. Click on the "Boot" tab and then check the option against "Safe mode" and click "Apply". Now restart the PC to boot in Safe mode.

Steps to boot the PC in Clean boot:

Once you have confirmed that the issue doesn't occur Safe mode, you can boot the PC in Clean boot as described in the following Microsoft KB article:

https://support.microsoft.com/en-us/kb/929135 

Once you have identified that a particular service is causing the issue, you can uninstall that software that service belongs to or install a more recent version of that software and check if the issue occurs.