This is getting off the Vista path, but since you asked... The concept is that malware written for Windows operating systems doesn't effect other operating systems like Linux. So while your Windows OS may not work properly (due to malware, misconfiguration, etc.), a Linux OS on the same machine can run with no problems. Of course if the problem is due to hardware issues, then neither will likely work.
Live Linux distributions (there are many) are packages which include enough of the Linux operating system to boot from a single disc (usually either a CD or DVD) You can pick them up in a number of places - some are included in magazines, available in bookstores, etc., for the price of the magazine. Many are available for free online. You download the disc image and burn it to your own CD/DVD.
Stick the disc in your optical drive (with boot order set to CD/DVD drive first), hit the power button, and a few minutes later (usually much quicker than Windows loads) you are faced with configuration screens (time zone, video display, etc) and then get a functioning desktop with web browser, media player, word processor, spreadsheet.... Different distributions vary with what's included, but I hope this is enough for you to get the picture.
Much more than this should probably be discussed over in the Operating Systems - Forums - Linux & Unix area. I will give you this much...
The distribution I am currently using is called Puppy Linux. Designed to support 'older' hardware and run completely from a CD which is loaded into RAM. You can save settings and personal info on your hard drive or say a USB drive, but if you choose not to you exit and there is no trace of it on the machine (good for public access machines or 'just to see what it's like'). If you're interested, click here
, Wary 5.0 is the current 'stable' release (Linux systems are continually going through development). As I said, Puppy Linux is just one of many 'distros' available.