Why can't Windows XP find text in my .WXP files?

Microsoft changed the Windows Explorer file searching facility in Windows XP so that it only searches files whose filename extension is registered with Windows as supporting searching. There is a Microsoft Knowledge Base article on this issue.

EXP versions 3.0 through 5.0.2 are affected by this design change.

To correct this problem for EXP, perform the following steps:

Right-click here and choose Save Target As from the popup menu to download the file ScanWXP_reg.txt to a folder on your computer.
Using Windows, navigate to the folder in which you stored the file.
Rename the file from "ScanWXP_reg.txt" to "ScanWXP.reg".
(This naming trick is necessary because Internet browsers block the .reg extension.)
Right-click the file ScanWXP.reg and choose Merge from the popup menu.
This merges the information into the Registry of your Windows system.
Log off; then log back on again.

Windows XP should now be able to find text contained in .wxp files.