Hi,
may be your hard disk got bad sectors, so every time you switch on the computer, system check the hard disk.
may be casued by swithing off without properly shut down, or swith off the computer when hard disk is still running.
you can
first try fully scan disk from windows.
or re- FDISK hard disk and format hard disk, then reinstall windows system.
if problem is still there, check the hard disk, are there any bad sectors. if got, and you can't bear checking hard disk every time you swithc on the computer, then replace the hard disk.