In order to do this you may need to turn on XP's wireless zero configuration.

Start -> Run

Type in services.msc

Scroll down to Wireless Zero Configuration and select it.

You now have the option to Start the service.

You also need to change the Startup Type from Manual to Automatic

Action -> Properties

Click OK.

You can now use XP to manage your wireless connection

Please advise your operating system if not xp.  I assume it is considering the screenshots and issue.

Well doing the copy and paste of your friend's registery is not recommended, even if its the same system. Based on everything, it is probally safer to do a clean install and keep the tech guy away from locking down your system.  It most cases, it's not necessary to create these policy's.

But you could take a look here:

run -> gpedit.msc

1. Computer Configuration > Security Settings. You'll notice a node called Wireless Network (IEEE 802.11) Policies.

2. Right-click Wireless Network (IEEE 802.11) Policies

Whatever he did to lock it should be in there.

That's actually one of the first things I tried. Unfortunately it didn't work.

By the way;

My operating system is a fresh install of XP, which a tech guy locked down with the Group Policy editor.

I've managed to get rid of most of the lockdown, but while I was trying to do so, I stupidly copied a friend's (who had the same laptop with factory install) registry over mine.

Other than that, I don't have any idea what would cause the problems.

I just checked, that node doesn't exist.

After some Googling, it appears that it only exists in Windows Server 2003.

You probally read information regarding windows server 2003. 

Each user has their own profile and settings including internet settings. you need to set up the network configuration in each user profile...including installing the wireless drivers for each. Most have a properties box that can be accessed from the admin account " to allow all users.." when the wireless drivers were first installed.

Try this:
Run > gpedit.msc
User Configuration > Administrative Templates > Network > Network
Connections
Enable "Ability to Enable/Disable a LAN Connection

I do not understand why you can not just ask the person that locked your system to repair what they did.  This person that you claim to have locked the system should be held liable for these issues as they are responsible for locking it.  It makes no sense for a personal computer technician to even use the gpedit to lock it down to the point its unuseable.  This person clearly did not know what they were doing.  This sounds a little suspicious and I will end off here.