|Apparently X300 is a laptop model|
If you get the message when only the hub is plugged in, it's wiring is incompatible with the USB ports on your laptop - you can't use that hub with anything with your laptop. The fifth connection some USB ports have is not compatible with the purpose of the fifth connection used on some mboards.
External hard drives always require the maximum current be available from the USB port(s) you plug them into - in theory that's the standard max of 500ma from every USB port directly connected to the mboard - that's always the case with desktop mboards, but in real life some laptop directly connected to the mboard ports can't deliver that much current.
You are likely to have problems if you connect the external drive to a USB port in a hub that is multiple ports connected to only one USB port directly connected to the mboard, sometimes even if it is a "powered" hub that has it's own external power supply connected to it so every port in the hub can be supplied with up to 500ma.
Try the external hard drive directly connected to a USB port directly connected to the mboard - if it then works fine, whatever hub you are using is inadequate. If the external hub has a jack you can plug an external power adapter into, try doing that, but that may not be enough either. If it doesn't have a jack, you need to get yourself a "powered" hub that does have a jack and comes with an external power adapter, or that doesn't but you can use one with, which may still not be enough, or get yourself a PCMCIA or ExpressCard USB 2.0 controller adapter and use the USB ports in that for the external drive (in the case of those laptop adapters, you may still need an external power supply if more than one device is plugged into it - make sure it has a jack you can plug one into. On the other hand, PCI USB controller cards for a desktop computer can deliver 500ma from every port in them).
Or remove the hard drive and install it in another external case that DOES come with two USB cables or a Y cable and/or that has a jack you can plug an external power adapter into.
e.g. Vantec NexStar - has a Y cable, one USB connector of the two is pass through, and it has the jack for a 5v 1amp adapter.
Most 2.5" external drives come with two cables or a Y cable that allows you to connect to TWO USB ports on the computer so that the hard drive plus the external case's circuits can get enough current. Some come with a jack on the external case you can plug an external power adapter into if you need to.
2.5" hard drives alone often require 500ma while spinning up.
Apparently your WD Passport model has a cable that only has a mini USB connector and one regular USB connector, so it can't be connected to two USB ports, and it appears it does not come with an external power adapter. .
Does it have a jack you can plug an external power adapter into?
USB connected priniters, scanners, and multifunction printer/scanner/etc. devices require more current than most other USB devices do. If you plug in one of those into a hub of the type above it is NOT a good idea to plug an external drive into the same hub at the same time - unplug one or the other.
Simlarly, if you have more than one external hard drive, it's probably NOT a good idea to plug them both into a hub of that type at the same time.