The Elder Scrolls Adventures: Redguard Download... Now
Since the game is now considered a classic, it isn't available on modern launchers like Steam in a native format. The most reliable and "ready-to-play" versions are found here:
Also available, though users sometimes report that the GOG version is slightly more stable out of the box. The Elder Scrolls Adventures: Redguard Download...
If you find the original tank controls and low resolution too difficult, look up the "Redguard Unity" project. It's a fan-made engine port that aims to make the game playable in widescreen with modern mouse support. Since the game is now considered a classic,