Live CDs (and DVDs) are versatile tools, allowing you to boot into an operating system without installing anything to your hard drives. Let's take a closer look at the five most popular live CDs.

Photo by bulinna.

Earlier this week we asked you to tell us which live CD was your favorite. After tallying the votes we're back to share the top five contenders. The following tools are unique compared to many of our software Hive Fives in that they are entirely independent of the main operating system installed on the computer. Live CDs load into the memory and allow you to use operating systems and accompanying tools without having to perform a permanent installation on the machine.

Knoppix

Knoppix is a Debian-based Linux distribution and one of the first Linux live CDs that was available. While the Knoppix distribution is packed with open-source goodness, one of the most popular uses for Knoppix is recovering files from damaged drives. To that end Knoppix is packed with open-source applications for testing disk integrity, recovering files, reading corrupted drives, and more. There are a total of 2,000 programs packed into the disc covering everything from disc recovery to media playback.

Ultimate Boot CD 4 Windows

The Ultimate Boot CD 4 Windows has a familiar interface. If you're a Windows user, booting into a copy of Linux to get work done could be disorienting. The Ultimate Boot CD 4 Windows uses your Windows installation discs (only Windows XP and Windows Server 2003 are officially supported) to create a bootable version of Windows contained on a disc. Tons of quality Windows-based tools are included in the custom disc covering everything from backing up and cloning your discs to running diagnostics to partitioning and recovering data. Many of the tools on the disc are tools you may already be somewhat acquainted with, like UltraVNC, Recuva, and CCleaner. If you're looking for a well packed toolbox that keeps you firmly planted in a comfortable Windows environment, The Ultimate Boot CD 4 Windows is an excellent choice.

Puppy Linux

Puppy Linux belongs to the family of ultra small linux distributions. Weighing in at under 100MB, it can easily be loaded on everything from a CD to a USB drive. The user interface is friendly even for a non-Linux user, and the basic tools you need for partitioning and file recovery are readily available—although it's just as great for web browsing and basic computing. Puppy Linux also has a rather handy feature: If you burn it to a re-writable CD, you can save your user settings for your next session.

BackTrack

BackTrack isn't going to help you recover your lost vacation pictures, but it will make sure nobody can get into your network to steal them. Packed with 300 tools covering everything from packet sniffing to hot spot probing to brute force password attacks, BackTrack is live CD designed to facilitate penetration testing of computers and networks. Deployed by a skilled user, BackTrack will leave no corner of your computer and network security un-poked, scanned, prodded, and analyzed. If BackTrack was your friend, he'd be the friend who responded to you bragging about how secure your new house was by throwing a brick through the front window to prove otherwise. (You have weird friends.)

Ubuntu

Ubuntu's enormous popularity as the mainstream Linux distribution certainly helps bolster its rank among live CDs. Many a new user to Ubuntu has messed around with the operating system using a live CD before using that very same live CD to install the full operating system. Even if you don't intend to do a full install, just like Puppy Linux you can do all manner of computing tasks without leaving a trace on the computer you're using. The Ubuntu live CD comes packed with Open Office, Firefox, Pidgin, the BitTorrent client Transmission, and the open source image editor GIMP—a decent stable of tools for using Ubuntu as a portable computing platform.

The following live CDs are worthy of honorary mention: Ophcrack is an extremely efficient rainbow-table based Windows password cracker (here's how it works). Hiren's Boot CD is a DOS-based boot disk that is absolutely packed with utilities like Partition Magic, Disk Director Suite, and Norton Ghost. A final nod goes to Gparted, a tool incorporated into many of the above live CDs. GParted is robust disk partitioning tool for creating, destroying, organizing and mirroring hard disks.


The five and accompanying honorable mentions merely reflect the most popular portion of the live CD based tools out there.