YopYop, a new Nintendo DS emulator for Windows has been released a while ago. It currently runs only demos but it seems quite promising. Here is some information about it taken directly from the Readme file:
* follower 2CPUs
* direct DMA (not on VBlank or other)
* support only mode 0
* support of the sprites
* not of support of the wide pallets. - sorts bgs and sprites
* part of the SWI
* does not emulate commercial plays because mainly of the CARD_REG
* emulates rather well the demo of Weather but small Pb with the mouse (click below the menus)