Microsoft's Service Pack 3 for Office 2003 blocks you from opening certain file formats the software giant deems less secure - including its own.
The service pack will block access to files including some Office Excel 2003, MS Office PowerPoint 2003 and MS Office Word 2003, it has emerged, as well as Corel Draw formats.
Microsoft said: "By default, these file formats are blocked because they are less secure. They may pose a risk to you."
The software giant has provided a workaround for users who need to access such files but the default is to disable access.
The Service Pack launched in December.
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