How to Change Windows XP Limited User Account Into a Computer Administrator

One of the places I worked at a few hundreds of computers and it is shared by students. Each student has their own user who is a restricted user account. Sometimes the lecturer there will complain to me that the administrator password has been hacked and modified by the students. This can easily be done if they do not set the security password for BIOS and allows students to boot a computer with a CD that comes with a tool to reset local user account password.
When the teacher reported to me that the students managed to turn a limited user account into an administrator computer, my guess is the students reset the administrator password, login as admin and change the account type to administrator. Turn a limited account on a computer administrator, but I was wrong. It turns out that the students did not reset the admin password and they can do it without logging into Windows as administrator. After a little searching, I found a free tool that can change the Windows XP user account is limited to computer administrator.
PCLoginNow is easy to use tool to reset local administrator passwords and other account on Windows systems. No need to reinstall the system. This reset Windows passwords and Windows security settings instantly. All versions of Windows are completely supported. This is a great CD for Home users and Businesses. And most important, it is the most popular solution and is safe to delete your Windows password until now.
In addition to the password reset capabilities, PCLoginNow can also help you maintain, change accounts policy setting and properties. You can easily upgrade the general account to administrator level, lock or unlock those accounts you do not need anymore, And moreover, all this is done without booting your tedious, time-consuming Windows System.
PCLoginNow The most powerful feature is to support Syskey. SYSKEY is an optional feature since Windows NT 4.0 SP3. This is intended to protect against offline password cracking attacks so that the SAM database would remain secure, even if someone has a copy. Although the system registry is protected by Syskey, PCLoginNow can easily bypass this mechanism and reset the Windows password.
Just four simple steps required to activate a limited user account to the administrator. 1. Download PCLoginNow.
2. Burn the ISO image to CD / DVD.
3. Boot the computer with a CD / DVD.
4. Click the Next button when you see a message that says "PC Login Now! Ready to get started, please click NEXT to continue ..."
5. Select the Windows system found by PC Login Now program.
6. Select the user account that you want to edit, check "is Administrator" and click Next. Changes to the Administrator account User Limit
Change Limit User Account to Administrator
7. Reboot and the user's computer is now a local administrator.
I find this tool amazing because it can change the user from zero to hero. I understand that some students adventurous and want to install or configure the system the way they like it but they can not do with a limited user account. Therefore, they find a way to secretly upgrade their accounts are limited to local computer administrator and now they can do whatever they want. We can not set a BIOS password because if the students entered the wrong security password for 3 times, it will be locked and we had to call HP support and ask them to reset. If you have a way to prevent the students from editing user accounts without logging in as an administrator, please share with me.