DSx86 is a PC emulator for Nintendo DS. It’s purpose is to allow you to run old DOS games on your Nintendo DS game console.

Currently DSx86 emulates the following:

80186 processor (which is actually a 80286 processor without the protected mode stuff)
MCGA graphics adapter (a stripped-down VGA with a maximum resolution of 320×200)
SoundBlaster (including AdLib-compatible FM sounds) sound card
83-key US keyboard

Release notes:

Version 0.01 Alpha. Pretty much everything in it is still temporary or unfinished, but feel free to test it and report all problems you find! See the release notes!

News source: http://forum.gbadev.org/viewtopic.php?t=16956