Una vez que hayas descargado el archivo de instalación, sigue estos pasos:

AutoCAD versions from 2010 to 2020 were the last to officially support Windows 7 SP1. Minimum Requirements (AutoCAD 2020): RAM: 8GB (16GB recommended). Processor: 2.5 GHz or faster. Disk Space: 6.0 GB.

If you're interested in that works on older hardware, I’d be glad to write an interesting, informative piece about:

Intel Pentium 4, AMD Athlon Dual Core de 3.0 GHz o superior con tecnología SSE2.