|Not all USB ports you plug into will work with all USB devices.|
Plugging into a USB port in a USB hub may not work for some devices, even if the hub is"powered".
The wiring to front USB ports may inadequate for USB 2.0.
On a desktop computer, you may have an IRQ sharing problem you need to fix.
See response 3 in this:
That pointed to.......
"....I have an old Compaq xp machine that works great, the only problem is that my portable hard drive won't work on the usb 2.0 pci card that I had installed some time ago...."
If it is an actual USB 2.0 controller card and NOT a USB 2.0 HUB card (there used to be USB 1.x HUB cards but I've never heard of or come across a USB 2.0 one; a HUB card plugs into a USB header on the mboard - it doesn't have it's own USB controller) then if the Toshiba portable drive works when you plug it into a single USB port directly connected to the mboard of the laptop, then it should work fine plugged into the PCI card - each and every port in the card should be able supply the standard maximum 500ma - I suspect the card has a poor connection.
Try removing the AC power to the computer, removing the card, cleaning it's contacts with isopropyl (rubbing) alcohol, or methyl (wood) alcohol (gasline antifreeze), or ethyl (vodka) alcohol, installing the card making sure it's all the way down in it's slot, and try again.
2.5" hard drives always require at least 500ma of current - if plugged into a single USB port that port must be able to provide the full 500ma - if it can't then you must plug into two USB ports, or if the external drive has a jack, plug an external power adapter into the jack. The standard max of 500ma is supposed to be available from every USB port directly connected to the mboard - that's always the case with desktop mboards, and it's supposed to always be the case for a PCI USB controller card when you plug it into a desktop mboard, but in real life some laptop directly connected to the mboard ports can't deliver that much current, and PCMCIA and ExpressCard USB 2.0 controller cards you can get for laptops often cannot supply more than 500ma total for all the ports in the adapter unless an external power adapter is connected to them (some have jacks for that - they usually don't come with a power adapter if they do).
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.
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 Toshiba 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.
Does it have a jack you can plug an external power adapter into?
The Y cable you are ordering - I'm assuming it has two USB connectors for the end you plug into the computer - should allow the drive to work in more situations, as long as the two USB ports can provide at least 500ma total, but the drive still may not work properly plugged into a hub that is plugged into one USB port directly connected to the mboard, even if the hub is"powered" .
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.
How much is the cable costing you including shipping?
I bought an external enclosure locally last week for a 2.5" drive that came with a Y cable to connect it to two USB ports, one USB connector is pass through, AND it has a jack you can connect a 5v external adapter to - it's made by Vantec - $30 CD.