Operating System
According to Good Old Games, Baldur's Gate has been tested and works on Windows XP, Vista and Windows 7. The game also is compatible with 64-bit operating systems. However, the game was originally designed to run on Windows 98 and your particular computer setup may run into some problems. You can work around most of the problems by downloading and installing the game's final patch (v. 1.1.4315) and run the game in compatibility mode. You can find links for both fixes in the resources section.
Processor
Baldur's Gate requires a 166 MHz processor to run. The game's developers recommend using at least a 200 MHz processor to play the game, but users have reported being able to run the game with 120 MHz processors.
Memory
Baldur's Gate requires a computer with at least 16 MB of memory and the developer's recommend having at least 32 MB. Additional memory can help improve the game's performance and loading times.
Hard Drive Space
The game requires a minimum of 400 MB of hard drive space to install and run. The game's recommended install uses 600 MB of hard drive space. The full game install uses just under 2 GB of hard drive space which immensely speeds up load times and eliminates the need for using the game's CDs or DVD when playing. The required hard drive space for a full install might be an issue for a computer built around the time the game came out, but a modern computer should have plenty of space.
Video Card
Your computer should have at least a 2 MB video card to run Baldur's Gate, and a 4+ MB video card is recommended. The game's graphical effects are designed to be improved on larger video cards, so if you have the graphical powerhouse you can activate many of the game's additional effects and run it at a higher-than-intended screen resolution. Even the weakest of modern video cards can run the game without a problem.