Nice find — that’s exactly the kind of root cause many of us run into. Preview handlers and other shell extensions run inside Explorer’s process, so a buggy or heavyweight handler (especially for media/PDF/codecs) can make large folders hang or even crash. Disabling the Preview pane and auditing shell extensions is a proven fix. Good call.
If you want to share this as a short “how I fixed it” post, here’s a compact, safe checklist and a couple of extra tips you can add.
What you already did (good)
- Turned off the Preview pane / “Show preview handlers in preview pane” in Folder Options — this prevents Explorer from invoking preview handlers while selecting files.
- Used ShellExView to find and disable non‑Microsoft shell/preview/thumbnail handlers until the folder opens smoothly.
Suggested follow‑ups and checks (one‑by‑one; safe to try)
1) Disable preview pane (if not already)
- File Explorer → View → Show → uncheck Preview pane (Alt+P toggles it). This is the quickest test to confirm a preview handler is the problem.
2) Use ShellExView (NirSoft) to isolate the extension
- Run ShellExView as admin, sort by Company, then disable non‑Microsoft Preview/Thumbnail/ContextMenu handlers (do a handful at a time). Restart Explorer and retest. If the folder opens fine, re-enable gradually to find the culprit.
3) Try Autoruns if ShellExView doesn’t show everything
- Autoruns (Sysinternals) lists more shell/COM load points; use it to disable suspect shell extensions and preview handlers. Reboot or restart Explorer to test changes.
4) Clear thumbnail & Explorer cache
- Disk Cleanup or Settings → Storage → Temporary files → remove Thumbnails; also File Explorer Options → General → Clear File Explorer history. Corrupt thumbnails can crash thumbnail/preview handlers.
5) Check the Mark‑of‑the‑Web (MoTW) / Preview blocking (if previews are missing for downloaded files)
- Recent Windows security changes block the Preview pane for files tagged as “from the Internet.” For trusted downloaded files you can restore preview by Unblocking a file (Right‑click → Properties → check Unblock) or use PowerShell’s Unblock‑File for many files — but be cautious: unblocking removes a security marker.
6) Update or remove third‑party preview providers / codecs
- Common culprits: PDF preview handlers, media codecs, image viewers, or “QuickLook”‑style apps. Update to the latest vendor build or uninstall to test. Many Explorer crashes trace back to an outdated codec/handler.
7) Test in Clean Boot / Safe Mode
- If the issue persists, boot to a Clean Boot (disable non‑Microsoft services/startup) or Safe Mode to confirm third‑party software is the root cause.
8) If Explorer still crashes, collect logs
- Reproduce the crash, then check Event Viewer → Windows Logs → Application/System for Explorer errors; that error message and faulting module name can point to the offending DLL (preview handler or shell extension).
Safety & rollback
- Disable only one or a few extensions at a time so you can roll back easily. Create a restore point before mass disabling or editing registry/policies.
- Don’t mass‑unblock files unless you trust their sources — MoTW exists to reduce a credential‑leak attack surface.
If you want, I can:
- Walk you step‑by‑step through ShellExView actions (which items to disable first).
- Help interpret an Event Viewer crash entry if you paste the faulting-module name.
- Suggest likely culprits based on which file types caused your problem (e.g., PDF, .mp4, RAW images, etc..
Which file types were the worst for you (images, video, PDF, Office)? I’ll give targeted steps for those handlers.