Windows users are being warned to be on the lookout for a new virus sweeping through all variants of the operating system. "This one's big," a Microsoft spokesman advised early this morning. "It affects Windows 7, Vista, XP and all Server editions."

Known as RioPalof-2011, the virus is believed to affect a section of the operating system's Hypervisor known as the System Obstruction Layer - a management control routine concerned with CPU governance. According to researchers at Symantec Antivirus, the entire SOL just gets "blown away".

The results have been frightening.

"I usually switch on in the mornings, make a coffee, chat with workmates and read the paper while my computer boots," a user identified as AF told one of the many online support groups already srpinging up, "but today it was just ... there. Oh man, I'm going to have to do some work now."

Commented another: "It's like my PC was suddenly running Linux or something."

It's not just the threat to productivity that's disturbing. Even old machines are vulnerable. PC resellers across the States have suffered a marked a drop in sales as a result of the virus. "This is a disaster," commented one. "The economy's already in a tailspin and sales are down. The last thing we need is consumers discovering Windows 98 machines are still usable."

Microsoft have yet to officially comment on the virus alert other than hinting that this month's Patch Tuesday might become Patch Monday Evening, Latish.