Right click on desktop go to personalise and there is all your options. The bottom one should say screen resolution or something. Im not on vista right now. But it is deff the bottom one.

i already did that but nothing happened. anyway i just found out the vista business do not have media center. is there any alternative i can dwnload smilar to media center?

As a replacement for watching dvd's, movies etc? or the actual media center?

If for watching dvds i use VLC player. You can download it here: VLC media player - Open Source Multimedia Framework and Player

Vista Business does not have Media Center.
Check the difference between vista versions here.
Native Resolution.

Non native resolution is what you can set, when you uncheck the "Hide Modes that this monitor cannot display" control on your Display Settings (not available on TFT screens)