Depending on how the hard drive is wired, you may or may not be able to do this.
Since we know very little of the drive all we can do is guess.
For many external drives, the internal hard drive in them is a regular desktop or laptop hard drive, with the adequate connectors.
If you can successfully disassemble the external enclosure and remove the drive, the next point is to see what type of connectors the actual physical drive has. If it has the USB connections directly on it, then it won't make a difference whether it is in the enclosure or not.
If it has regular SATA connectors on it, then you will have to open your PC, and connect it to a free drive bay.
The drive will show up as a regular hard drive on your PC, say if your current HD is C: and your DVD drive is D: it will possibly show up as E: if it can be read and mounted. It will work like your current HD.
It will not be removable while the PC is turned on and of course the PC must be turned off before you attempt to attach it without the enclosure.
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Phil AKA Vacunita
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Ignorance is not necessarily Bliss, case in point:
Unknown has caused an Unknown Error on Unknown and must be shutdown to prevent damage to Unknown.
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