Microsoft has warned Windows users of three critical flaws in its software and urged them to install patches.
Most home computers use Windows software
The security holes affect the way Windows handles certain graphic files.
If left unplugged, they could allow hackers and virus writers to take control of personal computers remotely.
Users of Windows XP, Windows Server and an updated version of Windows 2000 are advised to install a patch, which can be downloaded from the Microsoft website.
Microsoft issued the patches as part of its monthly security bulletin, with the most serious of the flaws awarded a 'critical' status.
The latest warning is related to how the operating system renders the Windows Metafile (WMF) and Enhanced Metafile (EMF) image formats.
STAYING SAFE ONLINE
Install anti-virus software
Keep your anti-virus software up to date
Install a personal firewall
Use Windows updates to patch security holes
Do not open e-mail messages that look suspicious
Do not click on e-mail attachments you were not expecting
Two of them could potentially allow a hacker or virus writer to gain control over a Windows PC, and security experts believe they may be exploited.
"It wouldn't surprise me if this didn't get the interest of the hacker community," said Graham Cluley, senior technology consultant at net security firm Sophos.
"It is interesting because a hacker could either direct someone to a website containing one of these graphics or send an HTML e-mail containing one and that would be enough," he said.
Microsoft began its monthly security bulletin in 2003 to make it easier for users and those responsible for computer systems to install patches and keep track of issues in its software.