Will this build work fine?

Solution
You will not be able to install your old hard drive and boot from it
If the OS is windows 8 that you bought a disk of it might be able to self repair and boot .
But if it Win 8 from a computer you bought or any other version of windows it wont .

The build itself is pretty good . The only issue is the hard drive which is a 2.5 inch laptop drive . Use a 3.5 inch desktop drive like the WD blue or seagate barracuda

Yes it fits in the case
You will not be able to install your old hard drive and boot from it
If the OS is windows 8 that you bought a disk of it might be able to self repair and boot .
But if it Win 8 from a computer you bought or any other version of windows it wont .

The build itself is pretty good . The only issue is the hard drive which is a 2.5 inch laptop drive . Use a 3.5 inch desktop drive like the WD blue or seagate barracuda

Yes it fits in the case
 
Solution