Why am I only showing 122gb when I just installed a 500gb drive. I tried looking at the disk managment area and it's not even showing as unallocated space

If you're using windows 7, right click on my computer and choose "manage" then "disk management". There, you should see your external HDD. If it is indeed a 500GB HDD and assuming it is registered as D:, you should expect to see something like (D:) 230GB and 270GB unallocated on one of the disks.

If that's the case, you can go to D:, right click and choose extend volume. Then you can extend it up to the total storage available

Good luck hope this help

Install a partition manager program like
http://www.partition-tool.com/personal.htm
open it and you will see the entire hard disk. In there either create another partition in the unallocated space or add it to the D partition.

If it's unallocated, that means the space wasn't turned into a drive yet.
You need to partition the space, and create a drive.

What you need to do amounts to going to Disk Management, right clicking where it says "unallocated space", and say "create basic disk". Then just repeatedly hit next.

If you'd prefer a more lengthy guide, see this:
http://www.bleepingcomputer.com/tutorials/tutorial116.html

Firstly, make sure that all the cables are plugged in properly for power and USB data transfer. If it still doesn't show up after a few minutes, then Right-Click on My Computer (Vista & Win7 users will see it labeled Computer), then choose Manage, then choose Storage, Then Disk Managment. It will take a few seconds for your computer to fully load in the screen. At the top it should list your hard drive or hard drive partitions if you have more than one partition. Under that you will see Disk 0, Disk 1, and so on. Do you see any of these with a long black bar to the right of it with it labeled Unallocated Space inside the box area under the black bar? If not, then there is something severely wrong with your My Book or the power or USB cables to it, or your computer's USB port is burned out, try all of your USB ports just to be sure. If you do see a long black bar that says Unallocated Space underneath it, then this is likely your My Book. Unallocated Space means that the hard drive hasn't been formatted yet, or that it's partition has somehow been deleted. If you've used this external hard drive in the past to back things up on, then your data is lost because data can't be stored or retained on a hard drive that isn't formatted or partitioned. Be sure that the area of Unallocated Space is actually your My Book. It should show how much Unallocated Space there is, and your's should be reading between 300GB - 320GB. To get your computer to recognize your hard drive you will have to partition and format it. Right-click in the white area under the black bar and choose Create Simple Volume. Follow the steps thru and format the hard drive. After its formatted it should be recognized by your computer again.

youve just answered your own question simply tell **** management to perform these actions and its up and running. Right click on your drive to see these options in disk management
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Plz remember to vote

Then you need to go into Disk Management, right-click on the disk and format it.

Check your AHCI (or ACHI, can't remember) settings in your BIOS. Turn them off, use "standard pata mode" even though you're using a SATA drive, and try again.

i just fixed my usb 8 GB. It was all space unallocated.
and i just formated it with paragon partition manager. Now ir works fine

try going to your control panel/administrator tools then computer managment, look on the disk managment under storage. you might have to set it up in there or asign a drive letter to it.

hope it helps

This is because your bios is only configured to recognise up to 250Gb. what you need to do is download the latest bios updates for you mboard, install them on windows. then you shoud have no further problems with the HDD.