What exactly do you mean by "export"? You shouldn't have to do anything --
the files should look almost identical if you just open it in the different
versions. (PPT 2000 and 2003 use the same file format, so one can open the
other without jumping through any hoops.)
Now, if you just mean you're opening in the different versions and the same
file looks different, then we need to look at what exactly is different.
Assuming that PPT 2000 is on one computer and PPT 2003 is on another, my
first guess would be you have fonts missing on one or the other system. Go
to Format|Replace Fonts and check for question marks in front of any of the
fonts listed. If you see one, that font is missing, and PPT is substituting
another font for it (probably Arial or Times New Roman), which could make
title bars shift.
Regarding the missing background, that's very unusual, especially in PPT
2000. I would first make sure you have installed all service packs on each
version of PPT. If the problem still occurs, then how are you creating the
background, and which version are you creating it in?
Transparency added in PPT 2003 probably won't look right in PPT 2000, and if
you have used multiple masters in PPT 2003, there's a (very small) chance
they won't be visible in PPT 2000. Usually, though, multiple masters created
in PPT 2002 or 2003 are at least visible in PPT 2000, but they're not
editable.