docs: Add Windows client documentation and common error fix (#14787)

- Added comprehensive Windows client setup guide (docs/client-windows.md) - Documented the common "parameter is incorrect" error in troubleshooting.md - Added step-by-step solution for Windows networking stack reset - Included WireGuard setup instructions and common issues - Added Windows documentation links to README.md This addresses the frequently reported issue #1051 where Windows users encounter "parameter is incorrect" errors when connecting to Algo VPN. The fix involves resetting Windows networking components and has helped many users resolve their connection issues. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-authored-by: Claude <noreply@anthropic.com>

Author: dguido

README.md

@@ -121,7 +121,7 @@ WireGuard is used to provide VPN services on Android. Install the [WireGuard VPN
 
 WireGuard is used to provide VPN services on Windows. Algo generates a WireGuard configuration file, `wireguard/<username>.conf`, for each user defined in `config.cfg`.
 
-Install the [WireGuard VPN Client](https://www.wireguard.com/install/#windows-7-8-81-10-2012-2016-2019). Import the generated `wireguard/<username>.conf` file to your device, then setup a new connection with it.
+Install the [WireGuard VPN Client](https://www.wireguard.com/install/#windows-7-8-81-10-2012-2016-2019). Import the generated `wireguard/<username>.conf` file to your device, then setup a new connection with it. See the [Windows setup instructions](docs/client-windows.md) for more detailed walkthrough and troubleshooting.
 
 ### Linux WireGuard Clients
 
@@ -210,6 +210,7 @@ After this process completes, the Algo VPN server will contain only the users li
 * Deploy from a [Docker container](docs/deploy-from-docker.md)
 
 ### Setup VPN Clients to Connect to the Server
+* Setup [Windows](docs/client-windows.md) clients
 * Setup [Android](docs/client-android.md) clients
 * Setup [Linux](docs/client-linux.md) clients with Ansible
 * Setup Ubuntu clients to use [WireGuard](docs/client-linux-wireguard.md)

docs/client-windows.md

@@ -0,0 +1,95 @@
+# Windows Client Setup
+
+This guide will help you set up your Windows device to connect to your Algo VPN server.
+
+## Supported Versions
+
+- Windows 10 (all editions)
+- Windows 11 (all editions)
+- Windows Server 2016 and later
+
+## WireGuard Setup (Recommended)
+
+WireGuard is the recommended VPN protocol for Windows clients due to its simplicity and performance.
+
+### Installation
+
+1. Download and install the official [WireGuard client for Windows](https://www.wireguard.com/install/)
+2. Locate your configuration file: `configs/<server-ip>/wireguard/<username>.conf`
+3. In the WireGuard application, click "Import tunnel(s) from file"
+4. Select your `.conf` file and import it
+5. Click "Activate" to connect to your VPN
+
+### Alternative Import Methods
+
+- **QR Code**: If you have access to the QR code (`wireguard/<username>.png`), you can scan it using a mobile device first, then export the configuration
+- **Manual Entry**: You can create a new empty tunnel and paste the contents of your `.conf` file
+
+## IPsec/IKEv2 Setup (Legacy)
+
+While Algo supports IPsec/IKEv2, it requires PowerShell scripts for Windows setup. WireGuard is strongly recommended instead.
+
+If you must use IPsec:
+1. Locate the PowerShell setup script in your configs directory
+2. Run PowerShell as Administrator
+3. Execute the setup script
+4. The VPN connection will appear in Settings → Network & Internet → VPN
+
+## Troubleshooting
+
+### "The parameter is incorrect" Error
+
+This is a common error that occurs when trying to connect. See the [troubleshooting guide](troubleshooting.md#windows-the-parameter-is-incorrect-error-when-connecting) for the solution.
+
+### Connection Issues
+
+1. **Check Windows Firewall**: Ensure Windows Firewall isn't blocking the VPN connection
+2. **Verify Server Address**: Make sure the server IP/domain in your configuration is correct
+3. **Check Date/Time**: Ensure your system date and time are correct
+4. **Disable Other VPNs**: Disconnect from any other VPN services before connecting
+
+### WireGuard Specific Issues
+
+- **DNS Not Working**: Check if "Block untunneled traffic (kill-switch)" is enabled in tunnel settings
+- **Slow Performance**: Try reducing the MTU in the tunnel configuration (default is 1420)
+- **Can't Import Config**: Ensure the configuration file has a `.conf` extension
+
+### Performance Optimization
+
+1. **Use WireGuard**: It's significantly faster than IPsec on Windows
+2. **Close Unnecessary Apps**: Some antivirus or firewall software can slow down VPN connections
+3. **Check Network Adapter**: Update your network adapter drivers to the latest version
+
+## Advanced Configuration
+
+### Split Tunneling
+
+To exclude certain traffic from the VPN:
+1. Edit your WireGuard configuration file
+2. Modify the `AllowedIPs` line to exclude specific networks
+3. For example, to exclude local network: Remove `0.0.0.0/0` and add specific routes
+
+### Automatic Connection
+
+To connect automatically:
+1. Open WireGuard
+2. Select your tunnel
+3. Edit → Uncheck "On-demand activation"
+4. Windows will maintain the connection automatically
+
+### Multiple Servers
+
+You can import multiple `.conf` files for different Algo servers. Give each a descriptive name to distinguish them.
+
+## Security Notes
+
+- Keep your configuration files secure - they contain your private keys
+- Don't share your configuration with others
+- Each user should have their own unique configuration
+- Regularly update your WireGuard client for security patches
+
+## Need More Help?
+
+- Check the main [troubleshooting guide](troubleshooting.md)
+- Review [WireGuard documentation](https://www.wireguard.com/quickstart/)
+- [Create a discussion](https://github.com/trailofbits/algo/discussions) for help

docs/troubleshooting.md

@@ -19,6 +19,7 @@ First of all, check [this](https://github.com/trailofbits/algo#features) and ens
  * [Azure: The client xxx with object id xxx does not have authorization to perform action Microsoft.Resources/subscriptions/resourcegroups/write' over scope](#azure-deployment-permissions-error)
  * [Windows: The value of parameter linuxConfiguration.ssh.publicKeys.keyData is invalid](#windows-the-value-of-parameter-linuxconfigurationsshpublickeyskeydata-is-invalid)
  * [Docker: Failed to connect to the host via ssh](#docker-failed-to-connect-to-the-host-via-ssh)
+ * [Windows: "The parameter is incorrect" error when connecting](#windows-the-parameter-is-incorrect-error-when-connecting)
  * [Error: Failed to create symlinks for deploying to localhost](#error-failed-to-create-symlinks-for-deploying-to-localhost)
  * [Wireguard: Unable to find 'configs/...' in expected paths](#wireguard-unable-to-find-configs-in-expected-paths)
  * [Ubuntu Error: "unable to write 'random state'" when generating CA password](#ubuntu-error-unable-to-write-random-state-when-generating-ca-password)
@@ -294,6 +295,43 @@ You need to add the following to the ansible.cfg in repo root:
 control_path_dir=/dev/shm/ansible_control_path
 ```
 
+### Windows: "The parameter is incorrect" error when connecting
+
+When trying to connect to your Algo VPN on Windows 10/11, you may receive an error stating "The parameter is incorrect". This is a common issue that can usually be resolved by resetting your Windows networking stack.
+
+#### Solution
+
+1. **Clear the networking caches**
+ 
+ Open Command Prompt as Administrator (right-click on Command Prompt and select "Run as Administrator") and run these commands:
+ ```cmd
+ netsh int ip reset
+ netsh int ipv6 reset
+ netsh winsock reset
+ ```
+ 
+ Then restart your computer.
+
+2. **Reset Device Manager network adapters** (if step 1 doesn't work)
+ 
+ - Open Device Manager
+ - Find "Network Adapters"
+ - Uninstall all WAN Miniport drivers (IKEv2, IP, IPv6, etc.)
+ - Click Action → Scan for hardware changes
+ - The adapters you just uninstalled should reinstall automatically
+ 
+ Try connecting to the VPN again.
+
+#### What causes this issue?
+
+This error typically occurs when:
+- Windows networking stack becomes corrupted
+- After Windows updates that affect network drivers
+- When switching between different VPN configurations
+- After network-related software installations/uninstallations
+
+Note: This issue has been reported by many users and the above solution has proven effective in most cases.
+
 ### Error: Failed to create symlinks for deploying to localhost
 
 You tried to run Algo and you received an error like this one: