how to remove win2000

Have a little laptop,has/had win98…we decided to ‘add’ win2000…did ok & took up too much space…easy and kept my programs.
Last nite we,(my also novice gal and I),decided to do the ‘complete’install of win2000,hoping it would erase all previous and leave me eith just win2000…ok quit laughing and help me get this straightened out..!
Personally at this point I would be glad to loose both win2000…at startup I can choose between win2000…which only opens in a safemode type small screen-or-win2000 which I suppose was the first one we did,but it will not start…ok-
How do I loose all this extra data and get back to 1 OS….we have a win2000 pro disk,(ours),but not win98