Part of the file is missing. / The presentation cannot be opened because a part is missing or invalid.

What's actually wrong

A .pptx is really a ZIP archive of dozens of XML parts — slides, layouts, a content-types manifest, and relationship files that wire them together. This error means a required part is absent or truncated, almost always because a save was interrupted: a USB stick pulled before the write finished, a crash mid-save, or a partial download. The parts that did get written are usually intact, so partial-to-full recovery is realistic; how much depends on whether a core part or just one slide's part was lost.

Free fixes — try these first

1. If the file is on a USB drive, SD card, or network share, copy it to your local hard drive first and open the copy — the error sometimes comes from a flaky read, not real damage.
2. In PowerPoint go to File > Open > Browse, select the file once, click the arrow beside the Open button, and choose Open and Repair.
3. Open the file with LibreOffice Impress (free) — its importer is more forgiving of missing parts, and you can re-save whatever it loads as a fresh .pptx.
4. Rename a copy from .pptx to .zip and try to open the archive. If the ZIP opens, drag out the ppt/media folder to rescue every image and video; if even the ZIP won't open, the archive structure itself is damaged.
5. If the file was ever in OneDrive, SharePoint, or Dropbox, right-click it there and check Version history — an older intact version beats repairing a broken one.

If the free fixes fail

When the ZIP itself won't open or a core part like the content-types manifest is gone, every viewer fails at the same wall — that's structural damage, not content damage. Our analyzer rebuilds the archive structure and reconstructs missing manifest and relationship entries from the surviving parts, then shows exactly what percentage of your slides made it before you download.