b) Did you make any recent changes on your computer?
Try booting your computer in Safe Mode again and check.
To boot into safe mode, follow the below steps:
1. Remove all floppy disks, CDs, and DVDs from your computer, and then restart your computer.
Click the Start button, click the arrow next to the Lock button, and then click Restart.
2. Do one of the following:
• If your computer has a single operating system installed, press and hold the F8 key as your computer restarts. You need to press F8 before the Windows logo appears. If the Windows logo appears, you will need to try again by waiting until the Windows
logon prompt appears, and then shutting down and restarting your computer.
• If your computer has more than one operating system, use the arrow keys to highlight the operating system you want to start in safe mode, and then press F8.
3. On the Advanced Boot Options screen, use the arrow keys to highlight the safe mode option you want, and then press ENTER.
For more information about options, see Advanced startup options (including safe mode).
4. Log on to your computer with a user account that has administrator rights.
When your computer is in safe mode, you'll see the words Safe Mode in the corners of the display. To exit safe mode, restart your computer and let Windows start normally.
SFC /scannow is a super-useful command you can use in any Windows version. When the SFC (System File Checker) command is used with the /scannow switch, the tool will scan all of the important Windows files on your computer and replace them as necessary.
Missing and corrupt operating system files (like many DLL files) are arguably the biggest cause of major Windows issues.
Considering that, plus the fact that SFC /scannnow is completely automatic and very easy to use, the tool should usually be one of your first troubleshooting steps.
1. Click Start, click All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator. If you are prompted for an administrator password or for a confirmation, type the password, or click Allow
2. Type the following command, and then press ENTER: sfc /scannow
[The sfc /scannow command scans all protected system files and replaces incorrect versions with correct Microsoft versions.]
A message will appear stating that 'The system scan will begin'. Be patient because the scan may take some time
3. If any files require a replace SFC will replace them. You may be asked to insert your Win7 DVD for this process to continue
4. If everything is okay you should, after the scan, see the following message "Windows resource protection did not find any integrity violations"
5. After the scan has completed, close the command prompt window, restart the computer and check.
Also you need to update the display drivers on your computer and check if the issue gets resolved.
To do this follow these steps.
1. Click Start, type devmgmt.msc and hit enter.
2. On the “Device Manager” window, expand the “Display Adapters” item, right click on the sub item and then click “Update Driver”.
3. Restart the computer once the driver is updated.
Contact your hardware manufacturer’s website to update the latest drivers.
Thanks and Regards:
Suresh Kumar- Microsoft Support.
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