quake 3 on windows 7

i bought and downloaded quaKe 3 arena off of steam. it opens up fine but once i get to the starting menu it starts glitching and flashing retardedly.

Any solving this?

Do you get any kind of error messages as well? Have you tried playing the game in windows xp compatibility mode? To do the same, first of all install the game and then right click on the quake3.exe or game.exe and then go to its properties and here you will see a tab called "Compatability", click on it and then select windows xp and open the game, check if the game is opening properly now.