Russian security firm Kaspersky has produced a bootable Linux CD capable of mounting and disinfecting hard disks used by Windows PCs.
The ISO file seems to be freely available, although is tucked away on a part of the company's website that is pretty well hidden. This makes me suspect that it is not intended for general use.
Amed Kamal wrote about it a week ago, providing a direct link.
Using a rescue disc could improve the detection of threats that are usually hard to find and remove, such as rootkits. This is because the Windows operating system is not running - and rootkits hide by tricking the operating system.
UPDATE: There is a newer version available.