Google added native Office file support to Google Docs, without the need of converting anything. Works from mobile devices too. (Not sure if the latter rolled out already, or just coming very soon.) Anyway. Easier, better, faster than installing and using LibreOffice.
OpenOffice opens it perfectly. Yeah the one which comes with Ubuntu 10.04 LTS (any version above 3.0). You can install it without a worry. (Or try it with a live disc, don't install it, check the documents).
If OpenOffice fails, you can try SoftMaker. Its a very nice alternative, and its very cheap (although, its not free, but it worth the price). There is a trial version available, install it, check the docs (for me it works flawless, much faster than OpenOffice). (Best and only alternative to OpenOffice I guess.) (And no I'm not a man at them, not working for them. I just tried / checked all the alternatives on Linux and this seemed to be the best amongst them. You can also use it on Windows and Windows CE. No mac though.)