0x800B0100 TRUST_E_NOSIGNATURE Fix That Actually Works

This Error Makes Me Want to Throw My Laptop

You try to install a program or run a driver, and Windows throws back 0x800B0100 with the lovely message "No signature was present in the subject." I know that moment. You're not alone — this tripped me up the first time too.

But here's the thing: there's a fix that works 90% of the time, and it doesn't involve messing with group policies or disabling security features permanently. Let's get to it.

First, Try the Real Fix: Re-sign or Trust the File

The error means the file you're trying to run doesn't have a valid digital signature. Could be because the signature was stripped, corrupted, or the file was downloaded from a sketchy source. Here's what I do first:

1. Right-click the file (setup.exe, .msi, driver .inf, whatever) and choose Properties.
2. Go to the Digital Signatures tab. If the tab is missing or says "This digital signature is not valid," the file is unsigned.
3. If you trust the source, unblock the file: right-click the file, go to Properties > General, and at the bottom, check Unblock. Click OK.

That's the first step. If the file is from a reputable developer (like Adobe, Microsoft, or your own internal tool), this usually solves it. But if the file is unsigned because it's an older app or a custom script, you'll need the next fix.

The Real Fix: Add the File to the Trusted Publishers Store

Skip the registry hacks and group policy nonsense — they break things later. Instead, do this:

1. Open Command Prompt as Administrator (press Windows+X, then A).
2. Type this command, replacing C:\path\to\file.exe with your file's full path:

certutil -addstore -user TrustedPublisher "C:\path\to\file.exe"

Hit Enter. If it succeeds, you'll see "CertUtil: -addstore command completed successfully." Now try running the file again.

What this does: it adds the file's signing certificate (if it has one) to your user's Trusted Publishers store. Windows checks this store when verifying signatures. If the cert is there, the error goes away — even if the signature itself is weak or missing.

Why This Works (and Why Other Fixes Fail)

Windows trusts files from publishers you've explicitly approved. The Trusted Publishers store is like a VIP list. Adding the file there tells Windows: "This publisher is okay, even if the signature isn't perfect."

The common advice to disable driver signature enforcement or turn off SmartScreen is a lazy workaround. It leaves your system vulnerable. This method keeps security on while solving the specific trust issue.

One thing: this won't work if the file has no certificate at all — like some open-source tools that aren't signed. In that case, you'll need to accept the risk and run it manually (but I don't recommend that for system drivers).

Less Common Variations of This Error

You might see 0x800B0100 pop up in different places:

• Windows Update failing — Usually a corrupted system file. Run DISM /Online /Cleanup-Image /RestoreHealth then sfc /scannow.
• Driver installation fails — The driver .sys file is unsigned. You'll need to enable test signing mode (not ideal) or get a signed driver from the manufacturer.
• PowerShell scripts blocked — Run Set-ExecutionPolicy -ExecutionPolicy RemoteSigned but only for your user scope (-Scope CurrentUser).

I've also seen this error in legacy software from 2008-2012 that uses SHA-1 certificates. Windows 10/11 requires SHA-256. If that's your case, you'll need to update the software or use a compatibility shim (advanced, but possible).

How to Prevent This in the Future

Three things:

1. Download from official sources only. If you get a file from a mirror or torrent, check its digital signature before running. Right-click > Properties > Digital Signatures.
2. Keep your tools signed. If you develop scripts or drivers, sign them with a code signing certificate. It's cheap insurance.
3. Use SmartScreen properly. Don't disable it completely. Instead, if you trust a file, right-click and unblock it. SmartScreen will remember your choice.

One more thing: run certutil -store -user TrustedPublisher periodically to see who you've trusted. Remove any publishers you don't recognize. That keeps your VIP list clean.

That's it. You should be past the error now. If not, drop a comment — I'm still active on this blog's comments, and I'll help you dig deeper.