Office can open Open Document types pretty much universally. More complex formatting is generally screwed up though, just as it is when opening MS types in LibreOffice.
Did Office 2003 get the ODF plugin pushed to it over Windows Update? It's on the oldish side, but there are still a lot of people using it.
I remember Office 2007's ODT support being rather poor, too. Most documents I tried to put through it only came through with minimal formatting preserved.
I didn't start using Linux (and therefore LibreOffice) until after I stopped using Office 2003 on any computers, so I don't know about its support for ODT.
2007 did do fairly poorly from what I remember as well. 2010 though is much better; I go back and forth between those fairly regularly. Fonts are obviously an issue, and complex formatting isn't quite right all of the time, but each suite seems to open most of the other's file types fairly well.
Also need to make sure to explain about file formats, or chances are pretty good that they'll try to send a LibreOffice file to a MS Office user.