"Hey, there. I have trouble in accessing all hard drives on a Windows 8 computer. As shown in the following picture, when I double-click a drive, the Restrictions dialog pops up, explaining that this operation has been cancelled due to restrictions in effect on this computer. Can you tell me how to solve the problem?"
As far as the problem described above is concerned, someone else may have enabled the setting called "Prevent access to drives from My Computer" in the computer. If so, you can allow access to drives using the two ways illustrated below.
Video guide on how to allow access to hard drives on Windows 8:
Method 1: Choose "Do not restrict drives" option in the mentioned setting.
Step 1: Double-click the group policy shortcut on the desktop to get into the Local Group Policy Editor.
Tips: You can create such a shortcut by referring to How to Make A Group Policy Shortcut on Windows 8/8.1 Desktop.
Step 2: Find and double-tap Prevent access to drives from My Computer.
BTW, the setting is found according to the path of User Configuration/Administrative Templates/Windows Components/File Explorer/ Prevent access to drives from My Computer.
Step 3: After accessing the setting, choose Do not restrict drives in the option list, and tap OK.
Method 2: Disable or do not configure the "Prevent access to drives from My Computer" setting.
Step 1: Open the setting according to the steps described above.
Step 2: Select Disabled or Not Configured, and then click OK.