Downloading old R6 can be a bit overwhelming at first, so there is a video linked below to guide you through it! (Coming later this year!)
If you are more of a fan of textual guides however, you can find one below the video.

How to download Old Siege using SlejmUr's downloader

1. Find a drive/folder where you have ample disk space. Some versions of old siege are as large as 80-90 GB.

2. Create a folder but make sure there are no spaces in its name. As an example: ‘OldSiege’ instead of ‘Old Siege’.

3. Set up an exclusion in your Windows Defender and/or third-party antivirus for the folder you just created. (see Guide: Antivirus Exclusion)
   This is important as some files that are required to make the game work properly are flagged as viruses. See Why is my antivirus flagging files as malicious?

4. Go to this message in the Operation Throwback discord server. Inside of the #r6-downloader channel you can find a post labled with SlejmUr. Go ahead and download it to the folder you just created. // ADD LINK
   Some browsers will flag the download as malicious (see Why is my antivirus flagging files as malicious? for more context), and if it happens to you go ahead and follow the Guide: Disabling Browser Security.

5. Run the downloader and follow the instructions on the screen.

6. Enter the Game Downloader section.

7. Locate the version you wish to download and press it.

8. Inside of your newly created folder where you have put the downloader, there will be a Downloads folder. Inside of it you will find a folder for every old siege version you have downloaded so far.

9. Wait for the R6 Downloader to reach 100%!

How do I run the game now that it is downloaded?

In order to run the game, you will need to navigate to the folder where it is contained inside of the Downloads folder. Once there you look for either of these three files: (if you cannot see file extensions, go to View → Show File name extensions)

• RainbowSix.bat
• RainbowSixGame.exe
• RainbowSix.exe

If you have located multiple of the listed files, you shall run the one that is highest in the list. For example: If you find both RainbowSix.bat and RainbowSix.exe, you shall run RainbowSix.bat as it is listed higher.

And that should be it! If you encounter any errors starting the game, refer to the FAQ here. If the FAQ does not contain a solution for your issue, the solution listed does not work, or you have any other questions, make a post in the help forum in the Operation Throwback Discord server!