Microsoft issued three security warnings late Wednesday affecting its popular SQL Server database, Windows XP operating system, and Word and Excel applications.

The SQL Server flaw, which Microsoft deemed critical, is the most serious of the lot. Exploitation of the flaw would "allow a low-privileged user the ability to run, delete, insert or update Web tasks," according to Microsoft's security warning. The flaw affects SQL Server 2000 and SQL Server 7, as well as Microsoft Data Engine 1.0 and Microsoft Desktop Engine 2000, which are used by developers building software using Microsoft’s Visual Studio development tools.

Patches are available for the flaws for SQL Server 7 and SQL Server 2000. The patches also fix the flaw in Microsoft Data Engine and Desktop Engine.

The second flaw, which could expose information, affects seven versions of Word and Excel. For Windows, it impacts Word 97, 2000 and 2002 and Excel 2002. For the Macintosh, it affects Word 98, 2001 and X. The patch fixes a flaw that could let a hacker use Word or Excel documents to steal data stored in another file on the computer.

Microsoft Word and Excel use "field codes" for updating information, such as copyright or legal information, that is automatically inserted in the document. "Normally the user would be aware of these updates occurring. However, a specially crafted field code or external update can be used to trigger an update without any indication to the user," according to the security bulletin. "This could enable an attacker to create a document that, when opened, would update itself to include the contents of a file from the user’s local computer."

Microsoft ranked the problem as a moderate threat. Patches are available for Word 97; Word 2000; Word 2002; Excel 2002; and Word for Macintosh. Most of the patches require that the latest service pack or product update be installed first.

The final security warning focused on a flaw in Windows XP's help system that would let a hacker delete files on a user's system. Microsoft deemed the threat as moderate.

"A security vulnerability is present in the Windows XP version of Help and Support Center and results because a file intended only for use by the system is instead available for use by any Web page," according to the security alert. "The purpose of the file is to enable anonymous upload of hardware information, with the user’s permission, so that Microsoft can evaluate which devices users are not currently finding device drivers for."

The information is deleted after the attempted upload. The security flaw would allow a hacker to construct a Web page capable of extracting this information.

Systems running Windows XP with Service Pack 1 installed are not vulnerable to this problem. Service Pack 1 is the first collection of bug fixes and updates released by Microsoft for Windows XP. Separately, users could download patches for Windows XP and Windows XP 64-bit Edition.

Wednesday's warnings join a long list of recent Microsoft security alerts. Earlier this month, Microsoft also fixed other flaws affecting SQL Server and also all versions of Windows. Microsoft also issued a warning for Outlook Express. So far this year, Microsoft has issued 61 security warnings. That total is slightly more than the entire number of such alerts issued in 2001.

The new warnings also came the same day Microsoft acknowledged that a security breach opened access to a Web server used by 20,000 Windows beta testers. Microsoft advised the testers to change their passwords.

Since January, Microsoft has stepped up its efforts to squash security bugs, following a companywide e-mail sent by Chairman Bill Gates. The Microsoft chief made security the company's top priority, even more important than adding new features to software.