Why doesn't my SATA cased HD work on my asus Eee Pc?

Does your sata external hdd come with a special cable that splits into two usb jacks, one for power one for data ? it should

“link” www.circuit-finder.com/categories/pc-related/usb-devices/726/usb-power-injector-for-external-hard-drives

2nd pic

Is your drive bus-powered or line powered, i.e., does it have an external power supply, or does it derive all of its power from the USB? If it’s the latter, see @Odysseus answer. If your PC will not recognize it, but another PC does, there may be a problem with the port.

Ditto here. I have issues with my external CD burner when I decide to be lazy and only plug in one of the USB cables, thus starving it of power.