My Windows laptop refused to boot into Windows. The ominous error message was:

Windows could not start because the following file is missing or corrupt: \windows\system32\config\system

A quick Google suggested that the registry had been corrupted. I tried various things to recover the OS, including using the XP recovery console to manually restore a backup of the registry. It didn’t work.

No problem. I have a fairly paranoid back-up regime. All the important information on my laptop is also stored on my subversion server. I could just reformat the laptop, reinstall the applications (including subversion) and check out all the files again. Except that I hadn’t thought to include my wife’s files on the laptop in my back-up plans. Oops. After hours of making no progress recovering the data. I tried Knoppix. I got access to the data in not much longer than it took to download Knoppix.

Knoppix is a Linux distribution that can run from a CD (i.e. it doesn’t require installation on your harddisk). It is also capable of understanding Windows file systems. To use it:

Download the latest Knoppix CD .iso file (approx 700MB). Note – The DVD version is much larger. Burn the .iso to a CD, for example using the free Active ISO Burner. Boot the stricken machine from the Knoppix CD. You may need to change your system to BIOS to boot from the CD first. How you access the BIOS varies between machines. On my Toshiba laptop you press F2 as the system boots. Drag and drop data from the stricken machine to a USB harddisk or memory stick. Or copy to another machine using FTP from Knoppix. The Knoppix user interface is easy enough to use, even if you haven’t used Linux before.

Note that you don’t have to enter your Windows password to recover the files. This brings homw how easy it is to get data off a password protected Windows machine, if you have physical access to the machine. Another good reason to encrypt sensitive data on your laptop, for example using the free Truecrypt.

Thanks Knoppix! I’ve added you to my mental list of worthy software causes to make a small donation to one day. Obviously you need access to a functioning machine to do the above. So why not make a Knoppix CD now, while everything is fine? You never know when you might need it.

Further reading:

Life hacker: Rescue files with a boot CD