A text string search is restricted under a default XP installation.
Essentially Microsoft offered "handlers" for their own programs, set the specifications for an in text search handler, and left it to others to create handlers for non-Microsoft file extensions.
People have gone crazy over whether this is an assertion of Microsoft dominance and an attempt to assert Monopoly control, to a (I think) more reasonable argument that Microsoft does not want to be in the business of writing file handlers.
That is the background. Kelly Theriot, Doug Knox, and others have done what can be done to remove the restrictions under XP:
The terrific Kelly Theriot has been court recorder for the various ways to deal with this issue. The following is directly quoted from her site:
Go to Search/All Files and Folders/More Advanced Options/Change Indexing Service/Index unknown file types.
Search for All File Types (Line 136)
If this doesn't help...
Windows® XP has a known issue for not finding a number of File Types when you do a Search for Files "containing text" or using the "A word or phrase in the file" option. This can be remedied for many file types, but not all.
Download the VBS file below. Double click the file you just saved. You'll be prompted to enter a file extension. If the PersistentHandler value is correct, no changes will be made. If the PersistentHandler value exists, but is different, no changes will be made. If no PersistentHandler value exists, then it will be created.
Enable XP's Search to find text in files:
Manual Edit:
To resolve this problem for other file types, install a program that registers a filter for the file type that you want to search. If no program that provides a filter is available, you can use the plain text filter for a file type.
Go to Start/Run/Regedit and add a PersistentHandler key under the file type key in HKEY_CLASSES_ROOT and set its (Default) string value name to the following value: {5e941d80-bf96-11cd-b579-08002b30bfeb}
For example, to use the text filter provider for .pas files, the following registry setting should exist:
HKEY_CLASSES_ROOT\.zzz\PersistentHandler\(Default) = {5e941d80-bf96-11cd-b579-08002b30bfeb}
After you add this value to the registry, you must log off and then log back on to make the change take effect.
******** end Kelly Theriot quote
I do not think anyone is happy with the find text string feature of XP. Believe me when I tell you that it is not a technical issue at its core, but a legal one at its core. A text string search with certain file extensions required ridiculous licensing fees, or were in some cases absolutely denied.
Rather than go through the process of adding custom handlers, (albeit I do use the "all" registry patch from Kelly's site) I just use a different utility. In my case Agent Ransack, but I am very impressed with the Google Desktop freebie.