Detailed instructions how to go by updating your Bios:
The following utilities allow you to manage and update the motherboard
Basic Input/Output System (BIOS) setup.
1. ASUS AFUDOS (Updates the BIOS in DOS mode using a bootable
2. ASUS EZ Flash (Updates the BIOS using a floppy disk during POST.)
3. ASUS CrashFree BIOS 2 (Updates the BIOS using a bootable
floppy disk or the motherboard support CD when the BIOS file fails or
4. ASUS Update (Updates the BIOS in Windows® environment.)
, the easiest way is to use option 4. updating your motherboard Bios automatically from the internet using Asus Update utility in Windows environment (page 52 of motherboard user manual)
If you don't have the utility installed already, you could either download it's latest version from Asus website (depending on which system you're running >> https://www.asus.com/Motherboards/P5LD2VM_SE/HelpDesk_Download/) or install it from the motherboard support CDROM.
As a precaution while using in-windows Bios update not to interrupt the update process and avoid running any applications while it's being performed.