System: 24GB ram (16GB usable)

[dockpaul]

Hello,
I upgrade my memory from 6 to 24GB with Patriot 2 sets of 3 4GB sticks 1600MHz. To my asus P6TD deluxe. Computer only reads 24 but only 16 usable...??

 

[Chirag Borawake]

Which is your operating system? Does your motherboard support beyond 16GB?

 

[retired_59]

Which is your operating system? Does your motherboard support beyond 16GB?

Try reseating your ram,of course this is just a diagnostic suggestion to see if it will correct your problem.

 

[vitornob]

Maybe you using Windows 7 Home Premium 64 bits, don't you?

This OS is limited in 16GB usable memory.
Here's a list of limitations for 64 bits Windows 7:

Home Basic: 8GB
Home Premium: 16GB
Professional: 192GB
Enterprise: 192GB
Ultimate: 192GB

EDIT:
(Got info from Microsoft in this website: http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778%28v=vs.85%29.aspx)