refresh rate is to high
 

i am using fedora core 2. i have integrated intel 82845G graphics. i have to pass "acpi=off" to the kernel at boot time for the system to run correctly. when i run X my refresh rate is set to 1024*786 @ 87hz by defalt. 87hz is to high for my monitor.my monitors max is 85hz. when i try to lower the refresh rate to some thing like 75hz linux tells me the changes will take effect the next time i startX. i restart X and it runs at 640*480 @ 60hz. 800*600 and lower is too low rez for me and i cant stand 60hz.

not necessarily the hsync matters as well
and actually 1024x768x87hz is actually interlaced 43hz vsync if your screen flickers on every odd/even lines so you are still around 31.5khz hsync.

you can try xorg/xfree setup (xorgcfg/xf86cfg) and choose your monitor from there and try and choose your res.
also check the startx output for errors