it does that when you unplug ps3 before it shuts down. when turned on it says that hard drive is corrupted, press X and the hdd will be checked for errors.and after that it will turn on normally. there was no point in taking out the hard drive. it happen to me like a 100 times.
On very rare occasions, you need to boot ps3 into safe mode and "restore ps3 system"
1. Connect the PS3 to any display preferably using the HDMI output.
2. Connect the PS3 to a power source. Also make sure the PS3 is off and not started.
3. Hold the Power On button until you here a beep which should take no more than 7 secs and also resets the video settings BUT DON'T LEAVE PRESSING THE BUTTON. After almost 5 secs you will hear another beep. Now leave the power button. Your PS3 is shut downed now.
4. Repeat Step 3 once again , quickly.