Try again.You have do do it Two times.
It works like that: Press button and hold, you hear one beeps and ps3 turns on, you still hold the button and hear two peeps, the ps3 than turns off, dont release the button but move finger a litle bit, you will hear again one beeps and ps3 turns on, HOLD BUTTON and you will hear now 3 beeps and PS3 turns off NOW release button and ps3 will boot into rescue menu.
Hold the button for the whole procedure.
Every time i tryed it it need to be done for two times.First step you hear only two beeps but for the second time you than will hear 3 beeps.Belive my and dont give up.
To formatting hdd cant work becouse all necessary data will be in the NAND and only extracted to HDD.Even it is corrupted PS3 will say HDD neeed to be formatted.I dont know what goes wrong but theorie and logical thinking sayes that formatting hdd will not solve the problem.