The first concern should be what are those little darlings doing that is causing frequent re-installs of W98??!! When you fix that problem, ....!
When you went to re-install Win98, what exactly did you do prior to getting that message? The command interpreter is the DOS environment and is the file COMMAND.com. Do you have 2 or more Windows98 boot disks and possibly the one you used to start the install is missing that file?
A re-install of Windows98 can be done while running Windows, but this is often ineffective. It should be done using the boot disk and you must boot up to that floppy. And that floppy must have a command.com.
Are you doing a clean install? This means that you are deleting the Windows folder and then doing the install. A clean install is the only way to correct some problems that have to do with registry errors. Your kids don't know how to run regedit I hope, because they could easily bring their system to the no can boot situation very quickly.
Be aware that if you delete the Windows folder you are deleting all mail boxes and address book unless they have been moved out of the Windows folder.
How much memory do you have? Processor speed? Available disk space? And they probably have Internet access? Are they running a frequently updated anti-virus? Are they running a firewall? These are questions leading to finding out what is destroying the system!
When the boot process can't find command.com in the root of the A: floppy, then it wants you to tell the boot where the file is. But you have no way to find out where command.com is. Bring your Windows98se boot disk(s) to another system and make sure that there is a command.com. This assumes you are booting to the A: floppy. When booting to the C: partition, boot looks for command.com in the root of the C: partition which would be C:\COMMAND.COM. But if Windows is busted, you need to be booting to the floppy.
You can try entering C:\Windows because under Windows98se, that's where the command.com is and it's also in c:\.
Good luck
Chris C.
