how to strart a pc

Need more info here, Disk Read error means it can't access the boot disk, need background info. Did this happen out of no-where? What is the brand/model of the compute and hard drive? Try reseating the hard drive, try a different cable if a desktop PC. You should also do a drive test on it by booting off a utility disk like Hirens or Ultimate Boot CD and running one of the drive test programs they have to see if the hard drive is bad.