Microsoft OFFICE 2007 file convertion(encoding) problem?

The papers you're opening aren't Word doents, and word can't determine the character encoding of the doents, so Word wants to know what character encoding the doents are using. If we knew the doent type, maybe we could help you. (The filename extension might - but no guaranty - be a clue. About the only 100% certain way is for you to open the doent in a hex editor and have enough experience to recognize the encoding.) If the doents aren't in the Latin alphabet, all bets are off.