Help! My pc turn on then off then on with 4 beeps

[taha.jaiti]

I had this major problem when i turn my pc on it turns off after that turn on after 1 secconds it do 4 beeps i tried everything switching the rams resetting the BIOS i have hp compaq dc7900

 

[mbilal2]

Memory (RAM) failure is indicated by 4 short beeps in some motherboards and "System Timer Failure" in others. Test each ram module individually or replace them. Reset your CMOS either with the motherboard jumper or by removing the battery for 30 seconds. See if there is a BIOS update available.