Windows XP does not have a spreadsheet of it's own. If you do have one installed, it's from an instaalled application (Works? - possibly).
You can buy Excel on it's own - or better, as part of MS Office - then you also get Word, Outlook and other software.
Or better still, you could get Star Office, which has an Excel "look-alike" and compatible Spreadsheet - and other modules, at a much lower price.