Also if you know your next route to fly, it is useful for getting to grips with he direction of arrival and sometimes the layout of the aerodrome you're visiting.
To prepare for a crosscountry you can use the sim in Google Earth. Visuals are much better and more realistic than MS flight sim.
BTW, I used every version of MS FS from 98 to 2004. The last one ran on 2,5 MHz processor with 2GB RAM and Nvidia 7500 graphics couple of years ago. Good enough. I would recommend rather to invest in very good controls - yoke + pedals instead of computing power. The experience for me really started as I brought the controls.
Miroc