Yeah! Good luck finding a legal or safe copy of Office 2003 now that it's two versions obsolete.
Word 2010 can still write the old .doc document format, and Microsoft won't change that until at least the next version, which won't concern you if you get 2010. Frankly, I doubt they'll change it for another decade at least.
But you're going to have to either explicitly save each file as a Word 97-2003 Document or set that as the default save file type in the Word Options. Not a biggie, but something to remember.
Hope that helps.