Yes, me too. I looked it up a few months ago in the "Free Online Dictionary", that misleadingly present them as synonyms:
3.http://img.tfd.com/wn/10/65BE4-warrantee.gifwarrantee - a written assurance that some product or service will be provided or will meet certain specifications
guarantee,
warranty,
warrant
surety,
security - a guarantee that an obligation will be met
I understand now there's a subtle (?) legal difference.
Apart from legal obligations, there's also the point of morality, and what most customers would consider good or bad after sale service.