Undertale minimum requirements for Windows assume having at least Windows XP, Vista, 7, 8, or 10 operating system. The minimum RAM requirement is 2 GB. As for a graphics card, it should be 128MB. You also have to have 200 MB free disk space to install the game.
If you go for recommended requirements for Undertale for Windows, your operating system should be Windows XP, Vista, 7, or 10. Recommended CPU would be 2GHz+ CPU or equivalent. For RAM, it is recommended to have 3 GB or more. And video card — 512MB.