Windows prevents any files opening

Based on the symptoms, there are two likely issues:

1. Downloaded files are being blocked by Windows Attachment Manager / Mark of the Web (MOTW).
2. File associations for common types (like .exe, .zip) may be corrupted, causing them to open in Notepad.

Try the following steps in order.

1. Check Internet security settings for downloads

If file downloads are blocked at browser/Attachment Manager level, enabling downloads can help:

1. Press the Windows key, type inetcpl.cpl, and press Enter to open Internet Properties.
2. Go to the Security tab.
3. Select the Internet zone (globe icon) and click Custom level.
4. In Security Settings:
   • Scroll to Downloads > File download and select Enable.
   • Scroll to Miscellaneous > Launching applications and unsafe files and select Prompt (recommended).
5. Click OK, then OK again.

This ensures Windows is allowed to download files and prompt instead of silently blocking.

2. Unblock individual downloaded files

If Windows Security/Attachment Manager is marking files as unsafe, each file may need to be unblocked before opening:

1. In File Explorer, right‑click the downloaded file (for example, the BIOS ZIP).
2. Select Properties.
3. On the General tab, if there is an Unblock checkbox/button, select it.
4. Click Apply, then OK, and try opening the file again.

If this works for one file, repeat for other important downloads.

3. Remove the Internet security block (MOTW) from multiple files

If many files are affected and Properties does not let them be changed one by one, unblock them in bulk:

1. Create a folder such as C:\DownloadsFix.
2. Move the problematic downloaded files (ZIPs, installers, etc.) into this folder.
3. Open PowerShell as Administrator.
4. Run a command to unblock all files in that folder and its subfolders, for example:
   • Use Unblock-File recursively on that folder (as described in the referenced Q&A) to clear the Mark of the Web.
5. After unblocking, try opening the ZIP or installer again.
6. Check that the file is really a ZIP and not just opening with Notepad

If a genuine .zip file is opening in Notepad, the file association or extension handling may be wrong. Confirm:

1. In File Explorer, enable file name extensions (View > show file name extensions).
2. Verify that the BIOS file ends with .zip and not .txt or another extension.
3. If it is .zip but shows a Notepad icon, right‑click it, choose Open with, and select File Explorer or a ZIP tool.

If many executable/file types open in the wrong program, this can be caused by malware and corrupted associations.

5. Repair file associations if malware changed them

If opening .exe, .com, .bat, .cmd, .reg, or .zip files starts the wrong program or shows strange behavior, registry cleanup may be required:

1. Open Regedit (press Windows key, type regedit.exe, run as administrator).
2. Navigate to HKEY_CURRENT_USER\Software\Classes.
3. In the left pane, look for subkeys such as .exe, .com, .bat, .cmd, .reg, .regedit, secfile.
4. Right‑click each of these subkeys and select Delete, then OK.

This removes user‑level overrides so Windows can use the correct default associations again. This step is specifically recommended when malware has broken how .exe and related files open.

6. If antivirus is blocking with “virus scan failed” / “virus detected”

If the error is specifically “virus scan failed” or “virus detected” when downloading:

1. This is typically caused by antivirus, not Windows itself.
2. If absolutely sure the Acer BIOS file is legitimate and from the official site, temporarily disable virus scanning, download the file, then re‑enable scanning immediately after.
3. As a last resort, adjust Attachment Manager scanning via registry

If Attachment Manager is overly aggressive and other methods fail, the ScanWithAntiVirus policy can be adjusted:

1. Open Regedit.
2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies.
3. If there is no Attachments key, right‑click Policies > New > Key, name it Attachments.
4. Right‑click Attachments > New > DWORD (32‑bit) Value.
5. Name it ScanWithAntiVirus.

(Values for this setting control how Attachment Manager invokes antivirus; use with care and only if comfortable editing the registry.)

Always back up the registry before making changes, and only download BIOS and other critical files from the official vendor site.

References:

• Information about the Attachment Manager in Microsoft Windows
• When you open a file on a Windows based computer, the file may start a different program
• File Explorer automatically disables the preview feature for files downloaded from the internet
• Can't open images and videos I downloaded myself because they could be potentially harmful - Microsoft Q&A