Yea, Fedora Core 5 has known problems with ATi and nVidia video. First thing to do is boot* into runlevel 3 and do some updating;
yum update kernel (this should be done first)
yum update (to get the rest of the updates)
After rebooting the laptop hopefully the video problem is gone, but if not then boot or switch to runlevel 3 (Ctrl+Alt+F1), log on as root and type something like; init 3
Then as root type something like;
system-config-display --reconfigure --set resolution 800x600 --set depth 16
Hopefully this should get you a generic working X configuration. For now it seems that your best bet (since your using the 64-bit OS) is to install the drivers from ATI's web site;
http://www.ati.com/
Your laptop is very close to mine (Aspire 5000 series) and for the 1280x800 resolution I have in my xorg.conf file;
Code:
Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "LCD Panel 1280x800"
HorizSync 31.5 - 90.0
VertRefresh 60.0 - 60.0
Option "dpms"
EndSection
Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 16
Modes "1280x800" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 24
Modes "1280x800" "1024x768" "800x600" "640x480"
EndSubSection
If all else fails you can always try to configure your video to use the generic vesa card and driver. You may need to disable the hardware probing by udev and maybe kudzu for the video for this to work.
* In case you need he howto boot into runlevel 3;
When the grub splash screen is displayed press any key.
Select the Fedora Core boot choice and press the 'e' key
Select the line that starts with something like 'kernel /vmlinuz' and press the 'e' key again
At the end of the line add a space followed by the number three (3)
When done press the 'Enter' key followed by the 'b' key