Hi! I was sent a sample of the Harraps dictionary English-Spanish, I used the sample in my kindlee and I liked it. I decided to pay the 26 euros cost for it at Mobipocket and downloaded it, but when I put it into my kindle, the device couldn't read it. It tells me "if you downloaded this file from Amazon, try to download it again". I downloaded it several times (from Mobipocket, since Amazon does not sell it) but still I cannot use it. Please, help me!

Fact 1:
Sample books are compatible with Kindle because they are not crypted (they don't have DRM protection).
Fact 2:
Kindle uses basically same DRM protection that Mobipocket uses, but they are artificially made incompatible with each other. By other words Amazon don't want you to buy books from Mobipocket and use them in Kindle, because they want Mobipocket fade away.

That said, you have two options.
1. You can always ask for refund.
2. You can break DRM protection and use you book in Kindle. While this is possible (just search Internet) it is not legal in every country.