ATI Mobility Radeon X1400
Linux X.Org driver
Display on the internal LCD works as long as you set the monitor settings correct.
External VGA port
Proprietary ATI driver
Proprietary fglrx driver seems not to support the X1x00 chip family (avivo).
# modprobe fglrx with driver version 8.23.7 or older reports "no such device".
Linux kernel Framebuffer driver