my computer misspells my words!

I have Windows XP, I.E. and Microsoft Works word processor.

When I write in the word processor, some words are changed to nonsense.

For example, today I wrote the word "chasmanthe" which is a type of plant. The WP changes it to "classmate" every time I right the word. Since I often write about plant names this is ridiculous. What I write is turned into nonsense by the word processor.