For the most part, on this blog, I try to convince readers to do something defensive on their computers - like a parent nagging a child to eat their vegetables. Only once have I put my foot down, so to speak, saying unequivocally last year that all Windows XP users should employ DropMyRights. Now, another emphatic endorsement - all Windows users should have a Linux Live CD, and, know how to use it.
If you're not familiar with the term "Live" applied to a CD, that's because it's not something that exists in the Windows world. Linux can do something Windows can't, run (not just install) from a CD. You can run Linux off a Live CD even on a computer that doesn't have an internal hard disk.
There isn't a single Linux Live CD any more than there is a single Linux. Live CDs were initially a great way to kick the tires on various Linux distributions. That still holds, but I suggest them for other reasons.
Have you ever panicked when Windows won't boot and you really need the files on the computer? You can boot from a Linux Live CD and easily copy files to an external hard disk, a USB flash drive or another computer on a Local Area Network. With a little work you should also be able to burn a CD or DVD. In the old days Linux struggled with the NTFS file system, but those days are long gone. Depending on the Linux distribution you chose, the hard disk may default to "read-only" mode, but this isn't a problem if all you want to do is copy files off the machine.
Speaking of the old days, Linux distributions used to have install CDs and Live CDs. Now, many CDs do both. Ubuntu, for example, introduced the ability to install onto the hard disk from the Live CD in version 6.06.
When Windows won't startup, the first debugging issue is always whether it's a hardware or software problem. Here too, a Live CD can help. If Linux boots and runs fine, and can see and view all the files on the hard disk, then you most likely have a software problem. If a Linux Live CD won't boot, there's a chance that it stumbled on some hardware it can't deal with. Therefore, it's best to boot with your chosen Live CD as you as you get it. If a previously tested Live CD no longer boots, you've probably got a hardware problem. No rocket science here.
If Windows is corrupted or infected with malware, a Linux Live CD can give it a new lease on life. Although running from a CD is much slower than running from an internal hard disk, the Live CD can restore Internet access. This is all but guaranteed for an Ethernet-based broadband connection and may even work for a WiFi connection.
The previously mentioned read-only mode for the hard disk can prove useful too. To some children, the web browser is the computer. You can set them loose on Firefox running off a Live CD and be 100% sure they won't screw up the installed copy of Windows in any way, shape or form.
A Live CD can also be used to fix a broken copy of Windows. Yes, Windows has a Recovery Console, but a Live CD has its pluses. For one, the Recovery Console is only an option if you have a Windows CD. Also, at least with XP, you have to provide an Administrator password to use the Recovery Console, not so with a Live CD. And, if the problem with Windows has to do with the part of the registry that stores passwords, you'll never be able to get into the Recovery Console. Plus, it's command line based whereas Live CDs offer a GUI. Finally, a Live CD offers many more options for copying files off the computer than does the Recovery Console.
Windows XP users may also appreciate that Linux Live CDs can be used to re-partition the hard disk, saving the cost of commercial products such as Partition Magic. I have to stress however, that any partitioning operation is dangerous, no matter what software is employed, and you should always backup everything you can think to backup before changing partitions.
As for cost, Linux Live CDs are free. You can download the Live CD for any number of Linux distributions as a single ISO file. Just burn it to a CD and you're done. Ubuntu goes ever further. If you don't have a broadband connection or can't burn your own CDs, Canonical will send you a free CD in the mail. For other ways to get it see here and here (look for the 8.04 LTS Desktop edition).
As with DropMyRights there is no down side to having a Linux Live CD at the ready.
The Live Ubuntu CD offers a very handy extra, a ram diagnostic program. Below you see the options presented when booting from the CD. The first option "Try Ubuntu without any change to your computer" runs Ubuntu from the CD. The fourth option "Test memory" invokes the Memtest86+ ram diagnostic.
When Windows is acting up, a ram diagnostic is always a good thing to try. Memtest86+ will run forever if you let it. I'd run it for about 8 hours. Look at the "Pass" and the "Errors" column. Eight hours should be enough time, on most computers, for quite a few passes through the ram. Needless to say, we want zero errors. They'll be hard to miss, Memtest86+ displays details about any errors in bright red.
Bought a new computer? A few hours worth of ram testing is highly recommended.
In researching this, I also tried the Linux Mint Live CD which seems like it provides access to Memtest86+. It didn't. In my virtual machine, the Live CD ISO booted straight to the Linux desktop. Likewise, the "hybrid" Live CD of Mandriva Linux 2008 Spring One also didn't offer a boot time menu, but instead booted to the desktop after asking some questions about my preferred language and country.
OpenSUSE version 11 has a boot menu that, like Ubuntu, offers a "Memory Test" (see below). It too invokes Memtest86+, in fact, it runs version 2.01 which is newer than the version included with Ubuntu 8.04.
The Linux user interface isn't all that different from Windows. Still, if you're allergic to Linux, or married to Microsoft, then check out the Ultimate Boot CD for Windows. It's the closest thing I've found to a Linux Live CD, in fact the price is the same: free.
The downside however, is that it requires a Windows XP or Server 2003 CD and support for Vista is far from complete. In a nutshell, its an XP thing. Also, there are a number of steps to creating the CD, it's more involved than simply burning an ISO file.
But, if you spend time with UBCD for Windows you can run assorted anti-malware programs from the CD you create to (hopefully) disinfect a copy of Windows. Even without anti-malware, it comes with a huge list of useful reporting and diagnostic programs. I was introduced to my favorite disk image backup program, Drive Image XML from Runtime Software by UBCD for Windows. If nothing else, it too, can be used to copy files off a computer when Windows won't boot. Highly recommended.