If you have a backup image of your drive,you need to go into the bios and change the boot order to cd/dvd drive first then hdd and then floppy if you have a floppy drive.
Press possibly F2 or the delete key..maybe a different key on startup and change the boot order and boot from your drive image if you have one.
Posting your PC's info would be a great help model/mobo/os etc
If you do not have an image of the drive,maybe a repair click here
You have what is commonly known as a looping system and a repair may be the best bet.