Operating system. laptop im using is acer aspire4720z intel pentium dualcore processor T2310

Question

laptop im using is acer aspire4720z intel pentium dualcore processor T2310 (1.46ghz,533msb,1mb l2cache).............so tell me how can i open bios setting.............becuz previous answer doesn't help me plz help me dude................because i want to reinstall my window xp..................i use esc,f1,f2,f12,del, but it doesn't help me.......