1) Fdisk is used to manage the partitions on a hard drive. If it cannot locate any fixed disks (meaning any hard drives), then you have an issue indeed! Check to make sure that the hard drives are detected by your BIOS, and that they have the proper master/slave relationship. You might also need to do a FDISK /MBR to reset the master boot record.
2) Missing Operating System is approapriate, as you just re-partitioned the disk, and that leaves all of the partitions on it unformatted and empty.
Now, how can you get both messages? Because your computer is trying to boot from somewhere. It cannot see the hard drive, doesn't find a CD-ROM or a floppy disk to work with, so it is asking you what you want to do.