Toshiba external hard disk cannot be installed properly

[help-me-pls]

Hello,
I've used my Toshiba external hard disk 3.0 1TB for a while already but suddenly it doesn't appear on my computer.
It does show up in the device manager.
I tried re-install it again but it said the device cannot be installed properly..
I'm currently using windows 7 32bit.
I've tried chkdsk on the command promp too but it said that "cannot open volume for direct access".
So, can anyone help me solving this? I can't format it coz I got really important stuff in it.

 

[RealBeast]

I would first try MBRWizard ( http://www.softpedia.com/get/System/Boot-Manager-Disk/MB-Wizard.shtml ) to repair the drive's MBR since it is probably a corrupt MBR from disconnecting or shutting down before a write finished.

Next I would try Recuva ( http://www.piriform.com/recuva ) to get the important files, and then never rely on an external drive again for important backup. Just scan this forum and see how many have these kinds of issues.