This article contains information about some Microsoft Office Project 2003 file formats that are blocked by default after you install Microsoft Office Project 2003 Service Pack 3 (SP3). You may also experience this behavior after you install an update that is released after Service Pack 3. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
By default, the following file formats are blocked in Project 2003 SP3:

•	.mpp Note By default, Microsoft Project 98 versions of .mpp files are blocked. However, Microsoft Project 2000 .mpp files, Microsoft Project 2002 .mpp files, and Microsoft Office Project 2003 .mpp files are not blocked.
•	.mpx
•	.xls
•	.txt
•	.csv
•	.htm
•	.html

The message that is displayed when you open a legacy file format depends on the legacy file format security setting. By default, the Do not load file with legacy or non default file formats in Project security option is enabled when you open a legacy file format in Project 2003. You will receive the following message when you try to save a file that is saved in a legacy format:Additionally, you will get the same message if you try and save a file in a legacy format, and this setting is enabled.

To enable the opening of files that are saved in previous Microsoft Project file formats, start Project, click Options on the Tools menu, click the Security tab, and then click Macro Security.

Additionally, you can modify the LegacyFiles registry entry to control the opening of these files in Project 2003. To do this, follow these steps:

1.	Click Start, click Run, type regedit, and then click OK.
2.	Click the following registry subkey: HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\MS Project\Security
3.	Double-click the LegacyFiles registry entry. Note By default, this registry entry is not created until you change the setting on the Security tab in the Options dialog box. Otherwise, this registry entry is not created until you manually create this DWORD value.
4.	Type one of the following values, and then click OK: • 0 This is the default value if the LegacyFiles registry entry does not exist. This value corresponds to the Do not load file with legacy or non default file formats in Project option in Project 2003. • 1 This value corresponds to the Prompt when loading files with legacy or non default file format option in Project 2003. • 2 This value corresponds to the Allow loading files with legacy or non default file formats option in Project 2003. This option is the default option in versions of Project 2003 that are earlier than Project 2003 SP3.
5.	Exit Registry Editor.