a visit to openoffice.org's home page is not very helpful, although the beta 3.2 is offered.
a visit to filehippo.com's home page will net you the 3.1.1 download towards the bottom left. from that download page, the technical tab includes windows 7.
i am using win 7 pro 64 and openoffice 3.1.1.
openoffice download comes with and uses java runtime environment. so, don't forget to get the latest java runtime environment while you're at filehippo.