easy question but im really in need of help

Hi i was wondering if anyone could help. Im trying to download a couple of games for my wee girls DS. I havent done this in a while and was on a different computer which was XP... now the computer im using is windows 7 and I cant seem to extract the files properly. Ive downloaded the games to the driver, which save as RAR files, I then compressed them into a folder and extracted all files in the folder... when putting into the DS it recognises the folders but not as a playable game format so im obviously doing something wrong.Can anyone advise me what im doing wrong and how to correct it? Thank you, so much appreciate any replies
Post Merge: [time]1274297142[/time]
anyone?? :(Just to add ive watched some youtube tutorials and i think the problem is that when ive downloaded the file it doesnt save as a compressed file dont know why?? Also just to say im using the R4

Downloading games should come in a .RAR format. In order to extract these properly, you'll need either 7-Zip or WinRAR.After extracting (Right click -> extract to...) you should have a .nfo and a .nds.Just put the .nds file into your games folder on the MSD card and it should be fine. Do not do any further compression.

Just download 7-zip(its free),then just right click and extract,just use the .nds part(you can re-name if you want,just have game name then .nds).
You may also want to look in a thread on this site for a ysmenu download,this enables a lot of the games that cannot be recognised on R4 to play.