Hi,
- Did you make any changes on the computer prior to the issue?
- Do you receive any error message?
Method 1:
Run the fix it and check.
Hardware devices are not working or are not detected in Windows
http://support.microsoft.com/mats/hardware_device_problems/
Method 2:
Step 1: Check if the issue occur on safe mode:
Start your computer in safe mode
http://windows.microsoft.com/en-us/windows7/Start-your-computer-in-safe-mode
Step 2: If the issue doesn't occur in safe mode then, try to perform a clean boot and check if any third party software is causing the issue.
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
http://support.microsoft.com/kb/929135
Note: After trouble shooting put the computer to start as usual by performing step 7 from the above Knowledge Base article.
Method 3:
You make sure that the computer have the latest update for the drivers from the manufacturer website.
“Update a driver for hardware that isn't working properly”
http://windows.microsoft.com/en-us/windows7/Update-a-driver-for-hardware-that-isnt-working-properly
Method 4:
Run a Microsoft safety scanner to make sure computer is free from virus infection:
http://www.microsoft.com/security/scanner/en-us/default.aspx
Disclaimer:
If you run the virus scan the program that is infected with virus will get deleted. So you have to reinstall the program. Also if the files and folders are affected with virus then they might even get deleted