External hard drive won't connect to computer

Format drive NTFS sounds like its corrupt, use mini partition wizard...
may also need 3TB Unlocker from manufacturer of Hdd

If you have a SimpleTech SimpleDrive connected to your computer and you're experiencing problems with the external hard drive, there may be several reasons why it's malfunctioning. Troubleshooting your computer can help rule out common problems and the possibility that the hard drive may be defective. If you recently purchased the device and suspect there is something wrong with it, return the defective drive to SimpleTech or the reseller for a replacement. Incompatible USB Port Problems SimpleTech SimpleDrive plug and play options makes it easy for you to connect the device to your computer. But you may encounter problems if your computer's USB (Universal Serial Bus) ports are not compatible with the external hard drive. Make sure your ports are powerful enough to operate the drive. USB 2.0 ports are recommended, but if you're using an older computer with 1.0 ports, the hard drive will function much slower or you may receive an error message that the device is not compatible with your system. b> Missing External Drive Letter If you're unable to find the SimpleTech external hard drive's letter on your desktop after you have installed the drivers for the device, it's possible that the external drive may be assigned to another drive. Sometimes, the hard drive is assigned to a network drive and you may need to manually change the drive's letter in Disk Management. b> SimpleTech SimpleDrive Incorrectly Formatted b> SimpleTech SimpleDrive is normally pre-formatted for Windows NTFS (New Technology File System), but Mac users may need to copy the backup software and reformat the external hard drive for FAT32 or Mac OS to be able to use the external drive. If the external hard drive is not formatted correctly for your system, it may not function or work properly. b> External Hard Drive Inaccessible If you receive an error message that says "Drive Inaccessible," the SimpleTech SimpleDrive may not be able to read the service area of the platter. If the external hard drive emits a loud or abnormal sound, this could mean the device is failing.
Test the drive on another computer to see if it is working properly. Otherwise, the external hard drive's surface area may be damaged or corrupted.
Replacing a Defective Hard Drive You can return a defective hard drive that is under warranty to SimpleTech. The manufacturer will exchange the device if the seal is not broken. But if you break or tear the seal on the case, any warranty claims will not be accepted and the device will be returned back to you. SimpleTech will only accept the device if you contracted a commercial data recovery company to retrieve critical data from the external hard drive and the seal needed to be broken. Before returning the defective drive, you will need to secure a RMA (Return Merchandise Authorization) approval number from SimpleTech and furnish any invoices or documentation regarding the data recovery company's services
or if its a usb external drive you might need a usb 3 card installed on your computer your computer might not have enough usb output power USB 3 card will provide more power when needed to the device to gain maximum throughput and conserve power when the device is connected but is idling http://blog.premiumusb.com/2010/09/usb-2-0-vs-usb-3-0/ these can be purchased on Ebay cheap and easy to install http://www.ebay.com.au/itm/PCI-e-PCI-Express-USB3-0-Card-new-NEC-720200AF1-chipset-/330608109325?pt=LH_DefaultDomain_0&hash=item4cf9c7670d for roughly $9 or $10free postage Hope this helps.

External hard drives not only provide additional storage space on a computer system but also allow data to be conveniently transported from one computer to another.

These drives typically plug right in to a port on the computer and function without any additional setup; however, if you are running into trouble where your external hard drive is not being detected, you must troubleshoot the situation to determine why the drive appears to be missing.

Check the USB connection running from the hard drive to your computer.

If the USB cable is not seated securely in the port, the computer will not detect the external drive.

Disconnect the USB cable from the computer and plug it into a different USB port. Occasionally, a USB port will fail to function with some hardware and changing the USB connection may correct this issue.

Switch from a USB to a Firewire cable connection, if possible.

The USB port on the hard drive may have died; if so, changing to a Firewire connection will resolve this issue.

Install the driver for the external device from the installation disc provided with the product. Older computer systems may require you to manually install this driver.

After inserting the installation CD, follow the prompts from the installation wizard to install the driver on your computer.

Restart the computer.

If you connected the external drive while the computer is powered down, it may not recognize the device when you turn on the computer.

After restarting the computer, connect the external drive to the system.

The drive should now be detected by your operating system.

Connect the external hard drive to a power source and then plug it into your PC computer using a USB or Firewire cable.

Log on to your PC computer using an account with administrative privileges.

Open the Start menu and click on the "Control Panel" icon.

Open the "Administrative Tools" folder and then double-click on the "Computer Management" icon.

Select "Disk Management" from the list of options on left side of the window.

Right-click on the drive you want your computer to recognize and select "Change Drive Letter and Paths."

Select a drive letter for the external hard drive to be recognized as and click "OK."

The drive will now appear in My Computer.

Hope this helps.

As virtualhost said, maybe you have not initialize this disk and partition it. Additional to disk mgmt, you could use this software

Try connecting the external hard drive to another computer to recover/backup your data.
When you have such a large capacity hard drive, it pays to have a second large capacity hard drive to backup your data in the event of the other hard drive dying.Hard drives do fail especially if you accidently drop it.

ry connecting the external hard drive to another computer to recover/backup your data.
When you have such a large capacity hard drive, it pays to have a second large capacity hard drive to backup your data in the event of the other hard drive dying.Hard drives do fail especially if you accidently drop it.

Get a new case and transfer the hard drive to the new case. You can get cases at any store that sells computer parts and several places online.
https://www.walmart.com/c/kp/external-hard-drive-enclosures

Please check you cable connection to your external hard drive. Try changing the cable.

If these drives are internally powered by the USB hub, two devices will not be recognised. ie: you can have as many pendrives as you like and they will be seen, because they draw little power from the hub, however, a larger external hard drive requires more power (some of these in fact have two usb connectors to power them). which is why your laptop will only recognise one drive at a time:

Solution: If you can get an externally powered usb drive, this should work.Another and possibly cheaper way would be to get an externally powered USB hub, which would solve the problem

Try connecting the drive to a different computer, to see if your computer is the problem.

If necessary, open the external case, and separate the disk-drive from the USB-to-disk-drive adapter.

Connect the disk-drive as a "slave" disk-drive in some computer, to see if the disk-drive itself still can be accessed.

If not, and you have "important" data on the disk-drive, search the Internet for a professional "Data Recovery Service" -- you ship your disk-drive to them, pay them a lot of money, and they repair the disk-drive, just long-enough to copy your files to a brand-new disk-drive.