Hi Naftali,
Did you check the Preferences settings for you Catalog on the PC?
It might be that the settings are set to use the Lightroom Database instead of saving as XMP
- Choose Edit > Catalog Settings (Windows) or Lightroom > Catalog Settings (Mac OS).
- Click the Metadata tab, and then do either of the following:
- To write adjustments and settings metadata to XMP, select Automatically Write Changes Into XMP.
- To write adjustments and settings metadata only to the catalog, deselect Automatically Write Changes Into XMP.
If you don’t write adjustments and settings metadata to XMP automatically, you can select a file and choose Metadata > Save Metadata To File.
- Adobe Photoshop Lightroom 4 * About metadata and XMP
Lets hope this helps to get the issue resolved.