First time at Downloading a rom onto Micro memory card... A little Stuck....

I Have just brought a DSTT chip for my NDS lite and a Micro Sd memory card..I tried down loading Dora puppy but when i download the file onto my pc it opens with Windows media player and it will copy onto my sd memory card but will not work on my Ds...I am from Australia can someone help??? My first time downloading a game from RomUlation.net.. I don't know if this is the right place to post this or if i am allowed... :-\

Is the file a .nds file? Have you formatted your card?

Yep I have formatted my Micro sd card.. where do i get the .nds file from???

What is the extension of the file you're copying? .doc, .nds, .rar, or what?

I am using a Vista on my desktop

That's not what I'm asking.
What is the file extension?
Word documents are .doc
Pictures are .jpg, .png, etc.
And this also has something.Look at this file in the folder and mess around with views until you see something like:
filename.xxx

Newer Windows OS by default hide known file types. Kaza likely cannot see them.Start here:
http://forum.romulation.net/index.php?topic=3880.0

when u first download a game from here it will most probably be a .rar file to make it to a .nds u need the program called WINrar(sorry cant offer link) to extract it once u have done that you'll have a folder with the .nds file and maybe a read me just put it on your micro SD with the software from devveloper and your good to go