how can i format my hard disk in fedora9 as ntfs or fat system?

search mkfs.vfat or mkfs.ntfs

Best regards

Be aware that those file systems do not implement account level access controls in a way that's compatible with Linux. FAT, in fact, has no access controls. So installing Fedora (or any other Linux) on a drive formatted as NTFS or FAT will greatly reduce your system security. (This lack of file security is one of several reasons that Windows(TM) systems are often labeled as "inherently insecure."

Note also that formatting a drive that contains an OS will, of course, erase that drive and all the data you have on it.

As a further point, it is much more common to format a partition than to format a drive. Actual drive formatting (usually called "low level formatting") is most often done by the drive manufacturer and remains fixed for the life of the drive. Low level formatting does not normally create any file system on the drive. It defines (and checks) the number of heads and cylinders, verifies the blocks, creates the initial "bad block" table, and sets up the "bad block" remapping areas.

I have quite a few older PCs that I am trying, without much luck so far, to install either gOS or Fedora Core. So far, I can't get the machines to recognize the disc. I am sure it is something easy I am missing. Do I need to fdisk the machine first? Help!

First, it's rather rude to hijack someone's thread to ask an unrelated question. You'll get better responses if you start your own thread.

Second, please read the "How to ask a question" guideline before starting your thread.

Specifically, other than the rudeness of butting in here, the "disk" to which you refer is somewhat ambiguous. From your mention of fdisk it seems as though you might be referring to the computer's hard drives, but a reference to, e.g., a CD drive also seems possible. If you have a CD drive on those old computers, I'd sugges you burn a copy of the System Rescue CD and boot from it. That will load an older Gentoo distribution from the CD, and you can use the tools on the CD to investigate your drives, etc., and establish exactly what you have in the "old" PCs. Depending on their age, the hard drives may use really old ATA controlers - the kind that came on a separate card, usually with a floppy disk controler included.

Anyhow, please start your own thread and provide LOTS of DETAILS about, precisly, you've got in those old boxes you're trying to use.