As Raoul mentions, NTBackup is not installed with XP Home. However, if you
have XP Pro, you'll find the shortcut under Accessories> System Tools. If
not found, you could reinstall NTBackup using Control Panel> Add/Remove
Programs> Add/Remove Windows Components.
In addition to the other advice, if you purchased a laptop
computer that did not come with a "real" XP CD-ROM
(a despicable, but growing practice), then you're just
out of luck -- you'll have to obtain third-party software
for doing backups.