Laptop wont turn on

my hp pavillion entertainment pc wont turn on it would just show a black screen while the lights by the keyboard stay on for awhile then turn off and turn back on again... i did try the

"*Take out the battery,
*Remove main supply,
*Hold power button down for 30 secs,
*Put only power supply in, do not put battery in
*Turn laptop on
*Put the battery in."

thing but its still doin the same thing... >_> can anybody please help me?? thx