You want a free office suite that is compatable with Microsoft Office.
You might want to check out Lotus Symphony

100,000 Register Lotus Symphony in First Week

"In just one week of availability, IBM's free office productivity
suite, Lotus Symphony, has been downloaded by more than 100,000
registered business and consumer users. The Lotus Symphony website
garnered more than a million visitors in the same time period.

The download figure is a record for IBM software."

(There may be some issues, but it is open document (the new format that
M$ has gone to) it generates PDF (Adobe squashed M$ from doing that
without a download - take that evil empire) but I have questions about
the compatability with older documents.

The article
http://www.systeminetwork.com/article/w/1001/n/5054/i/6823/a/55641/100_000_Regis\
ter_Lotus_Symphony_in_First_Week.html

The software
http://symphony.lotus.com/software/lotus/symphony/home.jspa