The theorectical speed of USB 1.1 is about 12MbPS. ATA100 and ATA133 are around 100MbPS. But a lot also depends on the environment that these drives are in, the bus speeds, etc.
but it is a bit strange that it doesnt show anything in an ext monitor. or does it now? if it does i guess the best thing you can do with it now is to use it as a desktop pc. if you dont find an identical laptop to replace the screen from.
Most of the time it is better to use an internal drive (Speed wise)
tho it is possible get high speeds with an external drive typically using USB 2.0 or firewire.