Tom called about associating files with programs…
http://support.microsoft.com/kb/307859
How to change file associations in Windows XP
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Article ID : 307859
To change file associations
1. Right-click a file with the extension whose association you want to change,
and then click Open With.
2. In the Open With dialog box, click the program where you want the file to open…
or click Browse to locate the program that you want.
3. Select the Always use the selected program to open this kind of file check box.