Hi Sarwar,
Are you using
BitLocker Drive Encryption to encrypt the drive?
As you are not able to see System and Security in Control Panel, I would suggest you follow the steps.
**a.**Open
Control Panel.
**b.**Under
Adjust your computer’s setting page, check if View by is selected as
Category.
**c.**Now check if you are able to see
System and Security.
If it still doesn’t show up, I would suggest you to run System File Checker scan (SFC scan)
on the computer which would scan for corrupt system files on the computer and replace them.
Use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7
**http://support.microsoft.com/kb/929833/en-us**
To decrypt the drive
If you are using Bit locker, I would suggest you to follow the steps.
a.
Right click the drive which you want to decrypt.
b.
Click
Turn off BitLocker. This opens the
BitLocker Drive Encryption dialog box. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
To decrypt the drive, click Decrypt the volume. To temporarily suspend
BitLocker, click
Suspend BitLocker Drive Encryption and then click Yes.
Refer:
Turning Off BitLocker Drive Encryption (Windows 7)
**http://technet.microsoft.com/en-us/library/ee424315(v=ws.10).aspx**
Also refer:
What's the difference between suspending BitLocker Drive Encryption and decrypting the drive?
**http://windows.microsoft.com/en-IN/windows7/Whats-the-difference-between-suspending-BitLocker-Drive-Encryption-and-decrypting-the-drive**
Bit Locker Drive Encryption in Windows 7: Frequently Asked Questions ******http://technet.microsoft.com/en-us/library/ee449438(WS.10).aspx**
Please let us know if the issue persists. We will be happy to assist you further.