Problem with screen size in X

[C & D Wyman]

Good day to all and happy new year, Over the holiday I decided to put together a Linux box. There's one problem I'm having, it seems that 640X480 is to big for my old Packard Bell monitor about 2 inches or so of the screen is above and below the monitor (vertical), my size side to side (horizontal) seems to be fine. I believe the problem lies with the monitor more than "X". Anyway is there a way I can compensate for this with my screen size. I adjusted the vertical knob as small as I could and it's not small enough. I am using a old VGA Packard bell monitor with a Asus mach64 video/sound card in a p120 with an asus mainboard with 32Mb RAM. I am using redhat 6.1 and I'm getting sick of typing for everything at the prompt.(If I'm not in xwindows the screen seems fine) I tried editing my xf86config file but couldn't find it in the traditional place ( /etc ? ). I'm stumped so any ideas would be terrific. Thanx in advance for any help.        --Chris