F-Secure Rescue CD is a bootable environment for removing deeply-embedded malware on a PC.
The package arrives as an ISO image, which means you'll need to create the bootable disc or USB key yourself. This isn't necessarily difficult - modern versions of Windows can burn ISOs to disc without any help - but it does assume more knowledge than some of the competition.
On the plus side, Rescue CD uses the Linux distro Knoppix, and does have a few features you won't always get elsewhere. You're able to apply proxy settings to help the system get online, for instance, and if it can't be repaired, it's possible to recover critical files to an external drive.
Beware: the CD manual has a worrying note which suggests it might break a working Windows installation to the point that it won't start any more, so it's probably best to use the system as a last resort only. Here's the relevant clause:
Using the Rescue CD on a working operating system may rename essential system files and so cause your operating system to no longer start. If this happens, you can use your system repair disk to reinstall the operating system. Note that this may reinstall a fresh operating system, which may remove any personal settings and files that you have.
F-Secure has good malware detection rates and just might get an infected PC working again, but beware, this kind of low-level scanning can also break a Windows installation in some circumstances. Use it as a last resort only.