MS DOS REFORMAT REInstlALING OPERATING SYSTEM!

Hey all.
I really need help, computer is compaq 5000 (desktop) don't have all the
details to it, as it's my sister's. But I can get them if needed! What i
do know is

That we had to reformat her hard drive thru msdos - because the recovery
disk wouldn't work, nothing worked - couldn't get into anything to do with
the computer (my computer/controlpanel, nothing at all) kept comin up with
some error) She has a 30gb hard drive, which was partioned...was windows
ME operation system.

So anyhow - we reformated, fdisked, repartioned it, try to boot up by floppy
and everything else (even recovery cd) - nothing has worked!!! In a last
hope, we tried to install 98 by boot disk, to see if that would work - Stil
NOTHING!

Just comes up with a A: promt thingy....but we can't do much from there.
We tried setup.exe, and all those things -but nothing.. We have looked at
various way to install it..tried many ways - nothing!

Can anyone give me an detailed way to do this? We are totally at lost, on
how to get this computer back up and running. I'm really hopein someone
knows what they are doing, cuz we don't anymore - we are at lost!

Thanks!!

Paula