My favourite internet security suite for Windows, with one of my favourite anti-virus engines. The product is moderately affordable, with a 3 PC licence.

Kaspersky Internet Security only works on Windows operating system, and has a few safe run / sandbox limitations on 64 bit computers. The safe run feature does work on 64 bit computers, but not as well as it does on 32 bit, hence the one point reduction on the "Range of extra features / functions".

The program is very easy to use, but you may want to avoid it if your computer is slow. This program will hog your CPU if your computer isn't fast enough to handle the processes, which come along with it.

The Kaspersky Update Folder can only be defragmented while the program isn't running. There are several other services, which prevent a complete defragmentation, unless they are closed. I prefer to defragment the computer in safe mode, to ensure the hard disks are defragmented properly; leaving very little if any fragmentation.

The program can be configured through the settings, to meet the users needs. The settings can then be saved to a configuration file, which can be imported later if the program is reinstalled, e.g. if you reinstall Windows and reinstall Kaspersky Internet Security. Its a lot quicker to import a configuration file, than manually reconfiguring the program.

The program can be installed on 64 bit machines, in which it installs to the "Program Files (x86)" directory. This doesn't limit the functionality of the program, all it means is that there's no build of this program at the moment designed to run only on 64 bit architecture.

Features include:
Virus scanner with 8,453,815 signatures (my update at about 4pm on 31 March 2012, i.e. the day I originally wrote this review on Ciao, under the same username as here).
Parental control, which seems standard as its available with most internet security suites.
Bootable Rescue CD, which you can download updates and burn onto CD, or run from a bootable USB flash drive.
Windows troubleshooting, to find faults caused by malware.
Privacy Cleaner, to delete browsing history, temporary files, etc.
Browser configuration for internet explorer, which can be used to check IE's security.
Application activity window, which displays running applications with network (including internet) access.
Network monitor displays applications accessing the internet, including the remote IP address they are accessing, and the received and transmitted data in bytes. You can also check for open ports, network traffic and blocked computers.
The virtual keyboard is a way to tackle the problem of key loggers, which somehow get past the real-time antivirus.
Safe run allows you to run your internet browser in sandbox mode, which is a securer form of private browsing.
A desktop sidebar gadget.

Program Settings:
General Settings is useful for password protecting the program, so it can't be closed and the settings can't be changed without entering the password. I recommend to set a password once you finish with all the other program settings, since it will keep prompting for a password every time you make a change to any setting.
There are 4 antivirus settings: File, Mail, Web, and IM.
You can use Application Control to control which applications have access to the internet.
System watcher allows you to roll back computer changes after a fault caused by malware.
Firewall, which is quite self-explanatory, setting rules to filter data packets, transfer direction, protocol, destination and ports.
Proactive defence, is extra antivirus defence with heuristic analysis, and leaves the decision to the user as to what should be done with the infected file.
Network attack blocker can be switched on to protect the system from malicious attacks, such as recurring ICMP packets in a DDoS from remote servers.
Anti-spam filters emails for junk.
Anti-banner can be used as an ad blocker, to block ads in all browsers without the need to install additional add-ons.