formatted ibm machine including dos

I have an IBM machine that has windows 98 which would not boot up right. I have a windows 98 disk so i could perform a fresh instal when I tried I got a ton of messages so not thinking I formatted c: drive which included DOS. Now All I get is the message invalid disk when no disks are in. I have tried to change the it so it would boot to A: drive still get the same message. What can I do? I cant even install dos. Please help