Modify shared memory in1520

Hi

 

I´m a new user of inspiron 1520 with nvida 8400m gs (128mb), 2GB RAM and Vista

 

In video properties I have:

 

Memoria de graficos disponible: 895 MB

Memoria dedicada de video: 128 MB

Memoria de video del sistema: 0 MB

Memoria compartida del sistema: 767 MB

 

I would like to change this values but I don´t know. I don´t want to share RAM memory  with viedo memory. I searched in BIOS values but I didn´t find anything

 

Thanks