If you have a win98 floppy handy and the laptop does have a floppy drive, just boot from the floppy, do "fdisk", and delete all partitions. Then perform an "fdisk/mbr", and everything should be gone. You can also get aefdisk (
www.aefdisk.com) and insert it in the diskette- you can now use "aefdisk/delall" and "aefdisk/mbr" saving much of the input with the MS fdisk. In fact, aefdisk should also be fine with an XP/ME bootdisk (their fdisk utility does NOT have an option for the /mbr switch).
Now boot from the 2000 CD, which will allow you to make new partitions and install 2000 on the laptop.
Just a warning though, 2000 may have issues with particular drivers for the laptop- you either have to keep some EOM driver diskettes handy and at bootup hit F6 and when prompted throw in the diskettes, so the drivers would be loaded and installed, or use XP, which are a worse OS, but have a much broader driver database.