emachine pc?

If there is no floppy, CD or DVD present and you get that message, your main hard drive is probably deffective. It may only be a bad boot sector, all the way up to a dead drive.

Try booting with an install CD/DVD in the CD or DVD drive. A Linux live CD is particularly good for that. You may be able to get one from some computer shops or you can download an iso that you can burn to a CD-R.
Use that to access your main drive. If you can see it's content, it mean that it's boot sector is bad or ereased.
If you can access it, but can't see it's content, it's root folder have been corrupted. In thise case, DON'T ATTEMPT TO use it. Most of it's content is still intact, but not visible.

Disconnect your actual drive, but leave it in the computer's case.
Get a new drive and install it in the computer.
Install your favorite operating system on the new drive.

If you where able to see the content of the original drive:
Power off. Reconnect the old drive. Boot the computer. The old drive should be visible and accessible. As it's reliability is now dubious, copy it's content to your new drive.

If you where unable to see the content but the drive repported as unformated:
Get and install some disk scanner. There are some free ones available but the best will cost you some.
Reconnect the old drive.
Execute the drive scanner on the old drive. It will attempt to find and recover all the files. It will also attempt to reconstruct the folder structure. That process can take several hours, so you need to be pacient.
That drive IS in prety bad shape. You MUST copy all recoverd files to another drive. Once all recoverable files have been copyed elsewhere, repartition, reformat, disconnect and remove the old drive. Label it as bad and dispose of it.

If the drive don't even spinn, or don't show up at all, it's dead. ALL of the files it contained are LOST. Some laboratory may be able to recover the content, but it can cost several $1000 with absolutely NO guaranty that any file will be recovered and useable.

Electro
November 2012

remove cd from drive and then try booting

pc
November 2012