How to fix /windows/system32/config/system misssing or corrupt WITHOUT XP Recovery CD

So I came across the dreaded /windows/system32/config/system file is misssing or corrupt recently and I didn't have my XP disk to hand.  No matter which Forum I went to or blog post I read, nobody really had a viable solution so I thought I would write up the guide myself.

Obviously you dont have the XP Recovery CD if you are reading this, but if you do then Microsoft's guide on MSDN is pretty thorough and worth reading, although this way is much quicker if you have what you need at hand.

What you need:

Because you don't have the Recovery disk you need some way of accessing the files on the hard drive, so I have suggested a few ways of doing so, there will be others and please comment if you know other simple ways of doing so

1. USB to SATA/IDE cable.  Because we are working with Windows XP there is a high chance you may still have a Hard Drive with an IDE interface so buy your cable accordingly.  There is a picture below to help if you are unsure. You will need a second PC to plug this into to allow you to access the files. (Cheap)
2. USB Caddy or Enclosure.  Again, ensure your Hard Drive interface matches that of the caddy otherwise it will not fit. SATA to SATA, IDE to IDE. You will then just need a USB to USB cable to connect the two. You will need a second PC to plug this into to allow you to access the files. (Cheap)
3. Download Windows Mini XP or Mini 7.  You will need to download a .iso file of either of these, they are available from many sources, one of which is Hirens Boot CD.  When you download it, use software like ImgBurn to burn it onto the CD.  When your computer is booting, go to set-up (usually pressing F2) and ensure that booting from CD is your first option. Once you boot from CD you should be working in a cut-down version of either of these operating systems and should have access to the files on your hard drive.  (Free)
4. Download Knoppix.  Knoppix is similar to using Mini Xp or Mini 7, it is just a small operating system that you can run from a CD.  So download the image (.iso file) and burn it to a CD using ImgBurn. Go to set-up (usually pressing F2) and ensure that booting from CD is your first option. Once you boot from CD you should be in an environment where you have access to your hard drive.  There are guides to downloading and burning Knoppix to a CD on the internet that will be helpful to you. (Free)

SATA Interface - Hard Drive

IDE Interface - Hard Drive

The Guide:

By this point, whatever method you choose to use, you should have access to the file-system.  Navigate to C:/System Volume Information  (Assuming C: is your drive letter).   This folder contains a folder with restore points from the past that will help you solve your problem.  If the folder is hidden, there is a guide at the end you can follow to make is visible.  You will then want to navigate to the _restore{ [letters & digits] } folder. Inside here you will see lots of folders beginning with RP followed by some digits. Navigate into any of these folders and you need to copy the following files:

1. _REGISTRY_MACHINE_SECURITY
2. _REGISTRY_MACHINE_SOFTWARE
3. _REGISTRY_MACHINE_SYSTEM
4. _REGISTRY_MACHINE_SAM
5. _REGISTRY_USER_.DEFAULT

Once you have copied these files you need to navigate to the /windows/system32/config/system folder and paste the files there.
If any of the following files exist, you should delete them:

1. SECURITY
2. SOFTWARE
3. SYSTEM
4. SAM
5. DEFAULT

You then want to rename the following:

1. _REGISTRY_USER_.DEFAULT to DEFAULT
2. _REGISTRY_MACHINE_SECURITY to SECURITY
3. _REGISTRY_MACHINE_SOFTWARE to SOFTWARE
4. _REGISTRY_MACHINE_SYSTEM to transparent
5. _REGISTRY_MACHINE_SAM to SAM

You can then reboot your machine.  You now want to boot to the Hard Drive so if you changed any settings in the BIOS Set-up then change them back.  You should successfully boot into Windows XP and everything should seem normal, but we now need to do a System Restore.  To do a system restore you:

1. Click Start, then click All Programs.
2. Click Accessories, then click System Tools.
3. Click System Restore, and then click Restore to a previous RestorePoint.
4. Choose a restore point, preferably not too far in the past otherwise your applications may all require updating or changing. It will not delete any of your data.

 Once the system restore has completed you should have a fully functioning machine again. 

Showing Hidden Files & Folders On Microsoft Windows XP Professional or Windows XP Home Edition:

1. Click Start,then My Computer.
2. On the Tools menu, click Folder Options.
3. On the View tab, click Show hidden files and folders.
4. Clear the Hide protected operating system files (Recommended) check box. Click Yes when you are prompted to confirm the change.
5. Click OK.