Microsoft has warned users that it will drop support for Office 2003 Service Pack 2 in three weeks.
The company has urged customers to upgrade to a newer service pack that was involved in a dust-up earlier this year over blocked file formats.
The company's policy is to support an Office service pack for 12 months after it releases a successor. Microsoft rolled out Office 2003 SP3 in September 2007. It always extends that 12-month period to the following month's second Tuesday, the day it usually issues security updates.
"Any security updates released on or before October 14 will support both Service Packs 2 and 3," said a Microsoft employee identified only as "David" on a company blog. "Security updates released after October 14 will support only Service Pack 3."
Microsoft has patched 14 vulnerabilities in Office 2003 SP2 in the past two months alone.
Office 2003 SP3 also made news earlier this year when Microsoft apologised to rival Corel for blocking some of that software developer's file formats on the grounds that they represented security risks.
Office 2003 SP3 instituted new security policies that automatically blocked a number of older file types, most of them Microsoft-designed formats, although some third-party formats were included in the ban.
Microsoft defended the move last January, when it said that "some older file formats are insecure" and that "the decision to block the formats is strictly to protect your machine from being compromised."
Users complained loudly on Microsoft's support forums soon after Office 2003 SP3 was issued.
Microsoft has urged users to update to SP3. The update, which is free to Office 2003 users, can be downloaded from Microsoft's site.
Although Microsoft launched Office 2007 in late 2006, it will continue to support Office 2003 until early April 2014, according to its product life cycle site.