its 64 bit

sql server uses maximum it want on 64-bit machine and reserve it even though its ideal.

when other applications on server needs memory it will release it ... so nothing to worry about it.

still if you dont want this to happen you can set max server memory option using sp_configure.

about your old server ..

It must be 32-bit server. in that case sql server maximum can use 2 GB memory unless you provide /3GB or /PAE option in boot.ini file