Internal hard disk for storage
there was some problem with booting from my hard disk inside the laptop and i changed to a new one and using the old one just like external. But it is extremely slow and am not able to copy or open some files randomly. I tried formatting and it didn't work.. Please help .
It definitely sounds like the old HDD is failing. Issues booting, slow performance, and errors with files are all symptoms of a failed or failing hard drive. As you have already formatted it and erased the data as well as any possible corruption, I doubt there is any hope in getting it to run correctly. You could try running "chkdsk #:\ /r" where # is the letter of the drive that is shows up as, but don't have high hopes.