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.

Changes:

Mouse emulation using the touchpad. If you have not mapped the SELECT key to a PC key, it works as a toggle to swap the screens so that you can use the stylys as a mouse directly on the emulated PC screen.
EMS memory increased to 1.5MB. Problems in the EMS memory access have not been fixed yet, so this version might run certain games (for example Wing Commander 2) worse than the previous version.
Proper DOS “System File Table” handling. This was needed for the file handle duplication functions, and this is also a requirement for improved DOS device handling (including console I/O) in upcoming versions. This also fixes problems with the 4DOS @select function.
Preliminary support for EGA mode 0x0E (640x200x16). Not properly tested, but some games might work in this mode.
Fixed a bug in Mode-X MOVSB opcode (MOO).
Fixed a bug in DOS CONSOLE INPUT function (Ultima V).
Fixed DUNE 2 save game problem.
Added opcode “repe scasw” down (for real this time!)
Ignore port 0xB8B I/O (GOBLINS, MOO INSTALL).
Support input from port 0x3CE (FD, MOO).
Added Mode-X opcodes LODSB and LODSW (MOO).
Several new EGA opcodes supported (BL, CARRIER, START, WARET, SH, WC1, B2, CALGAMES).
Support DOS functions 0x45 and 0x46 (DUP – DUPLICATE FILE HANDLE) (4DOS).
Support DOS functions 0x27 and 0x28 (RANDOM BLOCK I/O FROM FCB FILE) (Ultima II).

http://dsx86.patrickaalto.com/