Hello there,
You're going to want to use your system's local group policy to accomplish this task. If you are on shaky ground with this technology, it is best to back up your system prior to meddling with the local settings. You can only do this on Windows 7 Professional and greater. Home Premium and Home do not include this capability, as these systems are for stand-alone systems that will never connect to a server operating system.
I am including screenshots.
If in Windows 7 Professional or greater access Local Group Policy:
Enforce the Local Group Policy Setting to Hide User Accounts in Control Panel Go to Start -> gpedit.msc
Navigate to User Configuration -> Administrative Templates -> Control Panel -> "Hide specific Control Panel items"
Double-click on that option on the right.
Click "Enabled" and click "Show" under List of Disallowed Control Panel Options.
Enter the value: Microsoft.UserAccounts
Click OK to exit out of these dialogues.
Force a group policy update by launching cmd.exe
Go to Start -> Search -> cmd.exe and launch the command processor.
Type: gpupdate /force
Open Control Panel and User Accounts will be completely gone from the menu list.
To get it back, you will want to go back to gpedit.msc set the option to "Not Configured", force gpupdate again. If you re-open the control panel, you will be able to see User Accounts once again.
Notice that in the image above, User Accounts (which should be displayed under System using the icon view), is not present.
This option impedes launching User Accounts from Control Panel. It could still be launched using a command line with the right know-how. Most users, however, will not know how to bypass this functionality.
You can use Group Policy to only permit access to certain control panel items, as well as block access to Control Panel altogether.
Keep in mind that while group policy can be used to manage individual systems, its controls and functionality were primarily designed to work on the server level. These options could be used in a work environment, forced from the server, to enforce policies for a network of computers. Your options in managing the "Local Group Policy" are limited, but they would override server policies that are set for workstations if you connected to a Windows network through a domain controller.