Cpu making beeps and nothing appear on monitor

[electrolover]

Hello everybody, i have an msi 7392 motherboard, with 2 gb ddr2 ram, 500 gb hard disk, pentium dual core 2.8 with a 512 mb pci express graphic card..
Actalu the problem is that, when i turn on my computer, nothing appears on my monitor, i have checked every hardware in my cpu and all is fine but i don't khow why nothing is appearing in mo monitor, have even check the monitor and the monitor is also working...
the cpu makes a small beep continuously at about 10 second interval.. Can anybody help me please? Thxxx in advance..

 

[nikorr]

Did u just build it or upgrade it or it's out of the blue?

 

[electrolover]

actually i had build it, have use it for 18 month and now am getting this problem..

 

[nikorr]

What's the PSU?