Your system won't boot. You suspect a piece of mischievous software has fouled the hard disk's boot sector. More important, critical files are entombed on the hard drive. So you pop in a CD, boot into a rescue OS, and you are provided with a variety of tools for probing that otherwise inaccessible disk. Such is the purpose of system-rescue Linuxes. Two distributions of this sort are GParted Live and SystemRescueCD.
GParted Live, or GParted LiveCD, is more or less a runtime environment for GParted -- the Gnu Partition Editor. It includes a few additional applications, though only a few. GParted Live has no Web browser, nor is it clear how one would go about configuring an Ethernet card. The GParted Live engineers told me it was possible, and a better Ethernet configuration tool might be in GParted Live's future, but only if it would not add too much to the boot-image size. If you want an editor, you'll have to be satisfied with Vim or nano. (I am a big fan of nano.) But, this is definitely a system with a single goal in mind.
GParted Live is based on Debian Linux. Its ISO image is about 94MB, and it can be run in one of two configurations: normal, or the TORAM configuration. Running normally requires that the boot media (CD or pen drive) be available while running GParted Live applications. Execute in the TORAM configuration, and you can remove the boot media. There's a memory penalty in using the TORAM configuration. Normally, GParted Live can execute in 192MB; the TORAM takes an additional 100MB.
GParted Live supports a surprising variety of file systems; I counted 13, though some are supported as read-only. And it does provide some applications beyond GParted. At the top of the list is Midnight Commander, the quintessential text-based file-system explorer. GParted Live also provides TestDisk, a partition-recovery application that can rebuild fouled partition tables and resurrect deleted partitions, depending on the degree of damage to the partition. TestDisk understands FAT, FAT32, NTFS, ext2, ext3, and several other file systems. Finally, you'll find Partimage, a sort of partition-backup application that can copy a partition-image file, enabling you to archive and restore whole partitions.
GParted Live is definitely a minimalist system. For example, the window manager is Fluxbox, but I couldn't find any styles or themes on the Fluxbox menu; you are stuck with the default desktop and menu theme. This is by no means a strike against GParted Live; it makes no pretense of being anything other than a runtime environment for recovering lost data.