How do i get ms dos i dont see were i can buy it so do i download it?

I reformated a computer of mine and i need to install dos!

I have DOS 6.22 installation floppies, but you probably need 7.0+. Get a blank floppy, stick it in your drive, and type the following at the command prompt:
format A:/v:dos_boot/u/s/c
copy C:\windows\command\sys.com A:\/v

Next, boot your friend's computer from the floppy and once DOS finishes booting, type the following:
sys A:\ C:

Now all you've got left is to setup autoexec.bat and config.sys.

: I have DOS 6.22 installation floppies, but you probably need 7.0+. Get a blank floppy, stick it in your drive, and type the following at the command prompt:
: format A:/v:dos_boot/u/s/c
: copy C:\windows\command\sys.com A:\/v
:
: Next, boot your friend's computer from the floppy and once DOS finishes booting, type the following:
: sys A:\ C:
:
: Now all you've got left is to setup autoexec.bat and config.sys.
:


The message:
I NEED A FREE MSDOS OPPERATEING SYSTEM
from Bitdog, may have some answers for Tom Collins.