installing win xp home. it wont accept product key on bottom of laptop

Do you have the correct version? (XP Home instead of Pro, for example - your product key sticker should tell you.)
Is the disc you are trying to use OEM or DSP/FPP? Try using the disc you might have got with the laptop.
Otherwise you will have to hunt for an OEM version for the brand of laptop you are using, which really won't be worth the effort.
Either switch to Linux on that system, or update to a newer product.