Are you using a 64bit OS or a 32bit OS? I'm gonna bet that 90% chance you're using a 32bit OS, since they only support aroudn 4GB of memory (a little less). To use all 6GB, you must upgrade to a 64bit.
In what kind of system did you install the memory? Specs please?
Another possibility is that you are looking at the available memory and not the total memory. What is the total memory listed under Control panel, system? It should show the total memory and in parenthesis the usable memory if you are using integrated graphics. As already stated, 32 bit versions of Windows only support <4B of memory. You need a 64 bit version installed in order to see the extra 2 GB.
system type: 32-bit OS
Installed memory(RAM): 6.00GB (3.48 GB usable)
Processor: Intel(R) Core(TM) i5 CPU M460 @ 2.53GHz 2.53
I will try the 64-bit u guys suggested
i need 4GB min requirement for revit architecture @ 32bit,
64bit requires 8Gb so i will need 2gb more
what is the maximum RAM for 64bit?
my laptop is upgradable up to 32gb RAM
thank you very much
There's your problem! You are using a 32 bit OS, which only supports up to 4GB of RAM (a little less since the OS is using some) due to the 32 lanes. Even if you add more RAM, the OS can only use 4GB. You will have to upgrade to a 64bit OS to use the other 2GB of RAM. As for max RAM for 64bit, it is in theory 2^64 bytes, but no home computer can have that much, so the limitations usually fall on the motherboard max, which in your case is 32GB.