Can't launch MAME

[pinballdude]

OK, so I am stupid when it comes to computers.
I downloaded MAME. Downloaded Donkey Kong Jr & DK3 ROMs
Put both in the ROMs folder.
When I try to launch MAME, I get a message that games cannot
be found. What am I doing wrong?
I am wanting to try to get to know video game emulating (right word?)
and eventually make my own game system to put into a coin op cab.
I guess if I don't know how to do it I will never get the job done?
Help me educate myself here, please?
Terry

[honkey]

Find out which version of MAME you have (.144 is the most recent) and then check if your roms match the .144 roms. Also, make sure you have the parent rom for the games you want to play. (You can't play any Galaga games for example without having "Galaga Namco rev. B")