# Windows protected your PC: installing Scalpel > Windows SmartScreen shows Windows protected your PC the first time you open Scalpel. Why it appears, how to check the download, and how to run it. Source: https://scalpeltrade.com/guides/fix-smartscreen Guide 13.10, Troubleshooting. Beginner, 4 min read. Checked with Scalpel 1.12.8 on 2026-10-15. By Scalpel Team. **In short:** Scalpel for Windows is a portable exe that is not signed with a paid Microsoft certificate, so the first time you open it, Windows SmartScreen says "Windows protected your PC". Check the file came from scalpeltrade.com/download, then click **More info** and **Run anyway**. You only see this on the first run of a downloaded file: in-app updates are signed and verified by Scalpel itself and do not trigger it. SmartScreen warns about any program it has not seen many times before from a known, signed publisher. A small trading tool that ships every couple of weeks never builds that reputation, so the warning appears for everyone. It does not mean Windows found anything wrong with the file. ## Windows protected your PC The full text reads "Microsoft Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk." There is only a **Don't run** button until you click **More info**. *Screenshot: SmartScreen before and after **More info** (1): the app name, "Unknown publisher" and **Run anyway** (2). Simplified.* ## Check the download is genuine, then run it ### 1. Make sure it came from scalpeltrade.com Scalpel is only ever published at **scalpeltrade.com/download** (and the Download panel of your account page, which serves the same file). Never run a copy sent in a chat, posted on a forum or offered by another site. If you are not sure where your file came from, delete it and download it again. ### 2. Check the name and size The file is **Scalpel-windows-x64.exe**. The download page lists the current version and its size in millions of bytes, for example 28.4 MB. Right-click your file, choose **Properties**, and read the exact byte count in brackets after **Size**: 28,412,160 bytes is 28.4 million, a match. (The figure before the brackets is in Windows' own units and reads lower, so compare the bytes.) In the SmartScreen prompt, after **More info** (1), the **App** line shows the same file name. ### 3. Click More info, then Run anyway Click **More info** (1), check the **App** line, then click **Run anyway** (2). Scalpel opens to the licence screen ([guide 1.3](https://scalpeltrade.com/guides/activate-licence)). Windows normally does not ask again for this copy of the file. ### 4. Keep the exe where you want it There is no installer. Keep **Scalpel-windows-x64.exe** in a folder you own, such as your desktop or a Scalpel folder in Documents, so the updater can replace it later. Not in Program Files: Scalpel cannot update itself there. Settings, logs and the SIM ledger live in %APPDATA%\scalpel, not next to the exe. Full setup: [guide 1.1](https://scalpeltrade.com/guides/install-scalpel-windows). ## Why updates never show the warning After the first install, Scalpel updates itself ([guide 12.2](https://scalpeltrade.com/guides/updates)). Every release is signed with our own offline Ed25519 release key, and before installing, Scalpel checks that signature against a key built into the app, plus the file's exact size and SHA-256 checksum. A file that fails any check is deleted and never runs. Because the app writes the update itself, Windows does not mark it as downloaded from the internet, so SmartScreen does not look at it. That signature is the real proof of origin for updates: even a compromised download server could not ship you a file the app would accept. ## What can go wrong - **There is no Run anyway button.** On Windows 11, **Smart App Control** can be on. It blocks unsigned apps outright, with no option to run them. That is a Windows security setting (Windows Security, App and browser control); read Microsoft's notes before you change it, or ask us on Discord ([guide 12.6](https://scalpeltrade.com/guides/discord-support)). - **Your work computer blocks it.** Company-managed PCs often allow only approved software. Ask your IT team; there is no way around that from Scalpel. - **Microsoft Defender quarantines the file.** An unsigned app that downloads and replaces exes can occasionally trip antivirus heuristics. Download it again from scalpeltrade.com/download, and tell us on Discord with the version number so we can report the false positive to Microsoft. ## Questions **Is it safe to click Run anyway for Scalpel?** Yes, for a file you downloaded from scalpeltrade.com/download. The warning is about the missing paid certificate, not about anything Windows found in the file. Do not run copies from anywhere else. **Why is Scalpel not code signed?** A Windows code signing certificate is a recurring cost. Scalpel instead signs its updates with its own Ed25519 key, which the app checks before installing anything. **Will I see the warning after every update?** No. Only the first run of a file downloaded in a browser. In-app updates are verified by Scalpel and do not trigger SmartScreen. **How do I know my download is genuine?** It came from scalpeltrade.com/download, it is named Scalpel-windows-x64.exe, and its size in bytes matches the size on the download page.