If the DRAM LED is 'on' then upon posting the ASUS BIOS determined the RAM has a problem. The problem can originate from a few issues:
1. Incorrect DIMM slots:
1 stick: CPU: | -- | 4GB | -- | -- |
2 sticks: CPU: | -- | 2GB | -- | 2GB |
2. RAM is improperly seated in the DIMM slot, carefully remove the RAM using the release, examine both the DIMM slot(s) and Stick for problems or debris, reinsert and make certain the locking mechanism 'snaps' in to place.
3. Bad stick of RAM, if you have 2 sticks try 1 stick at a time.
4. Other issues: Bent CPU Pin(s), Grounding/Shorting: aftermarket HSF with metal backplate, or Case with punch-out 'standoff's' vs brass standoffs.