IF your PC is a few years old and you spend long periods of time connected to the Internet, the chances are you have been exposed to a virus.

Don't believe me? Get yourself a firewall and see how many times someone tries to access your system when you are on-line. Even worse, e-mail, that miracle of the 21st Century, is now the favourite way to spread cyber disease.

A friend who recently added up-to-date virus detection software to his four-year-old machine was shocked when it discovered more than 50 infected files and half a dozen viruses. The machine appeared to be OK but every e-mail he sent out was a source of further infection.

PC World, one of Britain's biggest computer retailers, reckons the number of virus infestations is on the increase.

More than half of Britain's 25.2 million households now own a PC and, with an estimated 55,000 known viruses roaming cyberspace, it is vitally important to make sure you are protected.

With the home PC user now spending an average of 2.5 hours a day online, those who are complacent about the threat are putting their IT systems at serious risk.

To help, PC World recently compiled a list of the top ten viruses to look out for this spring.

Of course, it also hopes tales of impending virus infection will have thousands of worried PC owners dashing to their local store looking to buy anti-virus software.

In most cases this is not necessary. Nearly every PC sold in the last five years has some form of anti-virus scanner. It's worth digging out the manuals that came with it and finding what kind is fitted to your PC.

If you are lucky and the vendor is still going, bringing your protection up to scratch may be a simple case of surfing to a website and downloading an update.

Be aware, however, that some manufacturers (most notably Norton) demand a fee for this.

Anyway - on with the top ten:

* Choke worm: A virus that sends itself through MSN Instant Messenger by using a variety of filenames, including ShootPresident BUSH.exe. When the file is sent, a message is sent along with it, usually something like "President Bush Shooter is a game that allows you to shoot Bush." If you get an e-mail like this - beware.

* VBS/Kakworm: One of the most well known of all infestations, Kak is a virus which exploits security vulnerabilities in Microsoft Internet Explorer and Microsoft Outlook. A dangerous aspect of this virus is the ability to continuously re-infect your computer if the preview panel is enabled and you browse between folders, specifically the 'sent' folder that happens to contain the virus within a message.

* SirCam: A network aware virus which arrives in an e-mail with a random subject which is identical to the attached filename. If the attachment is opened, the worm copies itself into the Windows system directory with the filename scam32.exe. This virus then sends itself and local documents to all email recipients found in the Windows Address Book.

* W9S.mtx: A virus which has the ability to block access to certain anti-virus web sites. When an attempt is made to access those sites, your web browser may crash. Sneaky.

* W32/Maaistr.B This uses a complex encryption technique to delete all .ntz files on a PC, overwrite the WIN.COM/NTLDR file at times, and send .gif files found on the local machine to others along with itself. Nasty.

* Nlmda: This is an e-mail virus which causes havoc on the web, by sending copies of itself and files plucked at random from your PC's hard drive to all addresses in your contacts book, including any embarrassing e-mails you'd rather the world didn't see!

* Minda: This virus can infect all unprotected users of Win9x/NT/2000/ME. Its main goal is simply to spread over the Internet and Intranet, infecting as many users as possible and creating so much traffic that networks are virtually unusable.

* Kakworm: This is a virus which exploits security vulnerabilities in Microsoft Internet Explorer and Microsoft Outlook.

* W32.Slrcam.Worm This is a mass-mailing virus which attempts to send itself and local documents to all users in the Windows Address Book. Aside from e-mail overloading, it may delete files and/or fill up hard disk space.

* Love Letter: Another famous bug, this virus will arrive in an email message with this format: Subject: "ILOVEYOU", Message: "Kindly check the attached LOVELETTER coming from me." This virus searches all drives connected to the host system and replaces .jpg and .jpeg files with copies of itself and adds the extension VBS to the original filename. After a short delay the worm also uses Microsoft Outlook to send copies of itself to all entries in the address book.

REVIEWS: The Shadow of Zorro. Publisher: Cryo. Format: PS2 and PC. Price: £39.99 (PS2)/£29.99 (PC)

WE'VE already had Spiderman, Batman, Superman, the Hulk, the Fantastic Four and the X-Men. Heck, even Blade managed to find his way into a video game and his comic series ended years ago.

The world of superhero video games is virtually exhausted. To the casual observer, there would seem to be nothing of note left to do.

Except, that is, the legend of Zorro, famous masked swordsman, swashbuckling hero and ladies' man extraordinaire.

Amazingly, this South American Robin Hood was created as recently as 1919 and his exploits were made famous in a series of cliff-hanging adventures shown on American TV during the 1950s. More recently, Latino hunk Antonio Banderas took on the dodgy mask for sword-swishing duties opposite the delectable Catherine Zeta Jones.

It all seems so obvious now - Zorro has the perfect ingredients for an action adventure video game.

The Shadow of Zorro marks the masked swordsman's first appearance in a video game and publisher Cryo is so proud that it has produced two versions of the same story for the PC and the PlayStation 2.

Sadly, the South American locale has been moved to 19th Century California where Zorro has chosen to hang up his mask, albeit temporarily.

When a new police chief arrives from San Pedro, our hero suspects him to be a notorious war criminal long thought to have been put to the sword. Naturally, his fears prove correct and before your hard disk has even warmed up it's time for some flashing blade-style action.

The developers have taken the Metal Gear Solid template and applied it to a similar game set in a different period of history. As Zorro, you have to sneak around a bit, polish off the bad guys with a devastating display of swordsmanship and rescue the goodies - and the damsel in distress, naturally.

Spread across 28 different levels and seven chapters, The Shadow of Zorro has a nicely pitched difficulty level that allows you to grow with the character.

Players who still struggle to master the controls and achieve the required level of skill can always tweak down the difficulty.

Cunningly, each challenge presents a number of options with no one solution clearly better than the other.

So Zorro can get stuck in with his trusty weapon or he can sneak away like a thief in the night ready to fight another day. Although predominantly a third person adventure, you can switch view points at certain times.

And lovers of the old TV series will be delighted to hear Zorro can still extinguish the candle flame with a deft sweep of his sword.

Adventure lovers won't be disappointed.