In this guide I'm going to do my best to give you the most straightforward, step-by-step process to enable a Linux computer (In this case, a Raspberry Pi 3) running X-Windows to remotely control the desktop of a Microsoft Windows desktop (Example shows Windows 7 Home Premium).
I'll assume you already have a Linux computer loaded and running your favorite flavor of Debian/Raspbian. My Pi 3 is running Rasbian Jessie.
I'll also assume you have a running copy of Windows (7 in my example) running on a different computer and BOTH the Linux and Windows computer are active on your network and working properly.
We'll start with the Windows setup...
Step 1: Windows Step 1: Enabling Windows Remote Desktop
1. Click the Start/Windows button and right click on Computer.
2. Left click to select Properties
3. In the window that pops up, take note of the computer's name. We'll need this later for the log in, if you have password protection enabled.
4. Click on Remote Settings
5. Check the box next to Allow Remote Assistance connections to this computer
6. Click the Advanced button
7. In this pop up window, check the box next to Allow this computer to be controlled remotely and click OK.
8. You can now close out all of the open windows we opened.
Step 2: Windows Step 2: Finding Your Local IP Address
1. Click the Start/Windows button and click in the search box at the bottom.
2. Type in cmd and hit enter.
3. This will open a shell terminal. Start by entering cd\ and hit enter to take you back to the C:\> prompt.
4. Type in ipconfig and hit enter.
5. This will display all network connections on the computer and their status. Look for the active connection with an IP address assigned. It will probably look something like 192.168.0.xxx or 192.168.1.xxx xxx being the last three potential digits of the address. Note this address. We'll need it for logging in later.
6. Close out the shell terminal window.
Step 3: Linux Step 1: Update Raspbian
We'll start by making sure you're running the latest version of Raspbian and all of your libraries are updated.
1. Open a terminal window
2. Run command: sudo apt-get update
Follow the prompts. This should only take a couple of minutes
3. When that has completed, run: sudo apt-get upgrade
Follow the prompts. Depending on how out-of-date your OS is, this could take a while. Mine was fairly new and still took 30 minutes.
4. After the update/upgrade has finished, reboot Linux, run: sudo reboot
Step 4: Linux Step 2: Install XRDP
Open a terminal widnows and install XRDP, run: sudo apt-get install xrdp
Follow the prompts.
Step 5: Linux Step 3: Install Remmina Remote Desktop
If you closed the terminal, open it back up and run: sudo apt-get install remmina
Follow the prompts.
Step 6: Linux Step 4: Run Remmina
1. Open a terminal window and run: remmina
2. A window should pop up. You only need to enter the Windows computer local IP in the box and click "Connect!"
If all installed correctly, you should see your Windows desktop pop up in a window. You may or may not have to use your Windows log in to access the desktop.
Step 7: Finished: You Did It!
Congratulations, you are now accessing your Windows desktop through a Linux computer!