First of all - get the correct power supply for the cortex! theres usually some on well known auction site or at least get one the correct volt/ampage.

I have 4 cortexes - 2 for each mixer desk, 3 ran harddrives ok without a powered hub, but the other just did not want to work properly without one!.

Personally i would forget all about using harddrives and use memory sticks, I use the kingston (genuine not the cheap ones) 128 gigs and they work beuatifully plus as no moving parts and if not using a keyboard you can hold the up n down arrows without the playing track faultering

make sure you have the latest firmware installed - its no longer on there website - if you message me your email addy i will try n find were i have stored the last update.