Because of a change in the way filters are loaded in Windows XP,
third-party single-threaded filters do not load. The Acrobat PDF iFilter is
an apartment model filter. Here is a workaround, but make sure you backup
your registry before attempting this.
1. Click Start, click Run, type "Regedit.exe" (without the quotation marks), and then click OK.
2. In the left pane of Registry Editor, right-click HKEY_CLASSES_ROOT, and then click Find.
3. In the "Find what" text box, type "pdffilt" (without the quotation marks).
4. In the right pane, right-click the ThreadingModel key, and then click Modify.
5. In the "Value data" text box, type "both" (without the quotation marks), and then click OK.
6. Locate the following key:
7. In the right pane, right-click the DLLsToRegister key, and then click Modify.
8. In the list of DLLs, select pdffilt.dll, and then press the DELETE key.
9. Click OK to close this window, and then click the Close button.
10. Restart Indexing Service.
11. Force a full rescan of the directory with the PDF files.
Jack Blalock (MS)
I haven't tried this, but it's worth remembering. Microsoft's indexing service is very raw in XP SP1.