Problems getting Windows on a computer: just MS DOS?

My dad tried to reformat a Windows 98 computer to give to my brother, however something went wrong, and windows will not go on the computer. Right now, when it starts up, there is nothing but a DOS like prompt on the screen. My brother (this is over the phone) tried the DIR *.* command and got nothing for c:drive, and a list for the a:drive (which has in it a windows boot disk apparently). Question is, he wants windows on the computer, and none of us is sure how to get it on there. I tried getting him to type "install" on the a: prompt, and I'm not sure if it worked or not. Anybody know? I'm not sure why the reformatting didn't work (perhaps my dad didn't have the disks or something, I didn't get the whole story unfortunetly).