By disassemble you mean to tear it down to it's bare components all the way down to it's spindle and then reconstituting it within another disk as repair parts? If so unless you know what you're doing, then no it's not a good idea.
If you're asking about breaking apart an external HDD enclosure to get at the HDD within to drop into the laptop, then it depends, if it's a 2.5" drive then perhaps it'd be possible. I say perhaps because an external HDD will logically contain important files which will be erased when you format and create partitions on it.
^ Best you just buy a 2.5" HDD and get that laptop up and running. Speaking of laptop, what is it's make and model?