A few days back I got a Dell Precision T7400 workstation, after I saw it only had 4GB of ram, I decided to buy an extra 7GB (1x4GB and 3x1GB). After I installed the ram modules, showed the following in windows: http://imgur.com/a/U6NNg (it's in dutch but you should get the point)

So I checked the bios and it was only showing 6GB instead of 11:
http://imgur.com/a/Uddet

I know it has to do something with the configuration, so I tried putting 1GB sticks in DIMM 1-4 and putting the 4GB stick in DIMM 4. But than it only shows 4GB. Can anybody help me with this?