I am now asking friends and family to keep a spare CD or USB Flash Drive on which to keep a LIVE version of a linux distribution, why do i do this? Well there are a few good reasons even for the most careful of users. 

If you are not sure what a LIVE CD is then please do check out the excellent article at Wikipedia here http://en.wikipedia.org/wiki/Live_CD

The first good reason is that booting from a LIVE CD into Linux eliminates any resident BOT's / Virus / Trojans that are resident on the PC, hence you can fire up the Linux version of the Firefox browser from the desktop and use online banking services without fear of ID theft via malicious programs, the LIVE CD gives you a clean system for short while where you can use online banking safely.

A good choice of a simple Live CD for these purposes is Ubuntu or gnewsense - link below

http://www.ubuntu.com/desktop/get-ubuntu/download

http://www.gnewsense.org/Main/Download

The second good reason is that just by using one these CD's you can make a judgement call on how your system performs with a another operating system active. If your system seems more speedy and somewhat 'quicker' than usual this MAY indicate the performance of the OS on hard disk may be hampered by an undiscovered BOT / Virus / Trojan that is supressing the locally installed Anti virus malware programs. Thus you can call in a security expert to take a look at your system to investigate further

The third good reason is that there are several great LIVE RESCUE CD's based on Linux that can BOOT, UPDATE the in built and free anti virus malware scanner programs and SCAN your system. This is great advantage as the normal bootup of your hard disk based operating system is bypassed and of course any sneaky bypassing of local security programs by BOT / Virus / Trojan cannot be activated. Thus the LIVE RESCUE CD can be more effective than scanning via programs resident on your hard drive. Great examples of LIVE RESCUE CD's are below

AVG Rescue CD - http://www.avg.com/us-en/avg-rescue-cd

FSecure Rescue CD - http://www.f-secure.com/en_EMEA-Labs/security-threats/tools/rescue-cd/

OpenDiagnostics - http://www.volatileminds.net/opendiagnostics/index.php/OpenDiagnostics_Live_CD

The last good reason to boot up into a LIVE CD is that you want to dispose of your computer or hard disk, there are some great programs that WIPE all the data in a secure manner from magnetic media like hard disks, thus the next person to use your PC simply can't obtain any sensitive information from it using disk recovery tools, which is favourite method of ID theives to steal your personal information, the best BOOT and BLAST CD in my opinion is DBAN, links below.

DBAN - http://www.dban.org/

All the information above is for systems that are your personal property at home or are not under the control of an IT department, otherwise always consult your local IT expert for best advice.