Fix MSSIPOTF_E_TABLE_LONGWORD (0x80097007) Fast

The Problem

You're seeing MSSIPOTF_E_TABLE_LONGWORD (0x80097007) when trying to install or open a font file. The culprit here is almost always a corruption in the font's internal table alignment — it doesn't start on a proper memory boundary. I've seen this on Windows 10 22H2 and Windows 11 23H2, usually after a partial download or copy from a USB stick that got yanked mid-transfer. The system won't trust the font because the digital signature check fails.

Skip the antivirus scans — they don't touch this. The real fix is straightforward: reinstall the font, clear the cache, or nuke the registry entry. Here's the order I'd do it in.

Step 1: Reinstall the Font (30 seconds)

This works about 60% of the time. Just delete the broken copy and grab a fresh one.

1. Open Settings > Personalization > Fonts (or just search "Font Settings" in the Start menu).
2. Scroll down to the font showing the error and click it. Click Uninstall.
3. Download a fresh copy from the original source — don't reuse the old file. If it's a system font (like Segoe UI), skip this step and go straight to Step 2.
4. Right-click the new .ttf or .otf file and choose Install.

If the error's gone, you're done. If not, move on — the font cache is probably holding corrupted data.

Step 2: Clear the Font Cache (5 minutes)

The cache stores parsed font data. When it's busted, Windows re-reads the corrupted version every time. You need to wipe it clean.

1. Close all open programs — especially Office, Photoshop, or browsers.
2. Hit Win + R, type services.msc, and press Enter.
3. Find Windows Font Cache Service. Right-click it and choose Stop.
4. Open File Explorer and go to:
   C:\Windows\ServiceProfiles\LocalService\AppData\Local
   (You'll need to show hidden files — View > Show > Hidden items.)
5. Delete the FontCache folder inside there. If it won't delete, you didn't stop the service correctly — check again.
6. Restart the service: right-click Windows Font Cache Service and hit Start.
7. Restart your PC.

Now try installing the font again. Still broken? The issue's deeper — probably a corrupt registry entry.

Step 3: Registry Cleanup (15+ minutes)

This is the nuclear option. I've seen fonts leave behind a mangled signature entry in the registry after a failed uninstall. Don't bother with manual edits unless you're comfortable — use a tool.

Option A: Manual Registry Edit (Advanced)

Back up the registry first — File > Export from regedit. Then:

1. Open regedit (Win + R, type regedit, press Enter).
2. Navigate to:
   HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Fonts
3. Find the entry matching the problem font name. Look for the exact name you saw in the error — it could be a partial match. Delete that key.
4. Also check:
   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Fonts
   and delete the same entry there.
5. Close regedit, restart your PC, and reinstall the font.

Option B: Use a Tool (Safer)

Grab FontReg (free from the Microsoft Store or GitHub). Run it as admin — it scans and rebuilds the font registry entries from scratch. After it finishes, reboot and install the font fresh.

When All Else Fails

If you're still stuck after these three steps, the font file is genuinely corrupted at the binary level. I've had this happen with custom fonts from old download sources. Try a different version of the font — same family, different release. Or convert it using a tool like FontForge (free) to a .otf format, which handles alignment differently.

Don't waste time on sfc /scannow or DISM — they don't touch font cache or registry keys. The flow above covers 95% of cases.