nba 2k9 ps3 problem?

i just got a ps3 and nba 2k9.. i took it to my friend's house to play cuz he has hdtv and mine's not. everything worked until i took to my house.. when i plug eerything in, the ps3 starts, but nothing shows on tv... why? i saw online its cuz u need to change the setting back, but i did, and i still see nothing on screen... what should i do? what's wrong?
my tv is triniton sony from 7 years ago...

Did you hold down the power button until you heard 2 beeps? Should take about 5 seconds.