Ok really there are only 2 DS emulators (others are so far worse then these, they dont get a mention).
Desmume = BEST DS emulator, period. To play it you need the very min of like a 2.0-2.2ghz dual core processor.
no$gba = can run on slower processors, but sucks so bad, crashes, not very compatible, not much customization.
So maybe get a pc that isnt 10+ years old? :3
i mean netbooks these days come with 1.6-1.8ghz dual cores (and why would you get a netbook for gaming? XD), any laptop or cheap desktop easily come with 2.0ghz+ dual cores these says for like $250-400 area.
On Desmume, there is not much for speed options. you can turn off fog under 3d settings (if done in game, you have to do a reset. or just change it b4 loading) and set frame skip to 1-2 ONLY. (other guy is dumb and has no idea what frame skip is, frame skip of 9 would make you lag worse as it skips 9 frames before displaying one....) that will net you a VERY little bit of speed.
Btw Abhishek i like how you link to VERY old outdated versions of the emulators.... like desmume is on 0.9.7 official, and has made lots of SVN after that, but those are just source code you have to build yourself.