SP2 can also be ordered on a CD or found on cover CDs with some consumer technology magazines.

BBC: Microsoft said it was crucial PC users update

The iTunes vulnerabilities were spotted by Kaspersky on the Mac OSX v10.5 and later, Windows 7, Vista, and Windows XP SP2.

FORBES: Apple's iTunes, QuickTime, High On Cyber Security Vulnerability List, Kasperky Lab Says

He stressed it was crucial that XP users, business and individual home users, switched on their auto-updated so that machines could download SP2.

BBC: Microsoft said it was crucial PC users update

According to the Microsoft Web site, the operating systems affected include Windows XP, Windows XP Service Pack 1, Windows 2000 SP2, Windows 2000 SP3 and Windows 2000 SP4.

CNN: Sasser worm rips through Internet

The SP2 update for those using the Home Edition of XP was made available last week as a "trial", said the spokesperson, but Microsoft did not make it available automatically to all until Wednesday.

BBC: Microsoft said it was crucial PC users update