Hello Snowy, welcome to the Seven Forums.
An in-place upgrade
is language dependable, the language of old OS and new OS have to match. You can not do an in-place upgrade, keeping your installed software, from XP to Seven. Seven is in-place upgradeable only from Vista.
So the answer to your question is YES, you can upgrade from English XP Pro to any version of Dutch Windows 7. You have only one option, to do a clean, custom install and this can be made with Upgrade version of Seven in any other language. Using an upgrade version to do a custom install in other language than the old Windows is always possible.
A bit confusing, I hope you can understand.