X-Plane 10 requires, at the minimum,
a 2 GHz, dual-core CPU,
2 GB of RAM,
a DVD-ROM, and
a DirectX 9.0c-capable video card with 128 MB of on-board, dedicated video RAM (VRAM). See here for graphics card compatibility.
However, for the best experience, we recommend the following:
a 3 GHz, multi-core CPU (or, even better, multiple processors),
4 GB of RAM,
a DVD-ROM, and
a DirectX 10-capable (DX11 preferred) video card with 1 GB of on-board, dedicated VRAM.