Hello Piggy,
With Open Office, you can save your documents in Microsoft Word format. You should do this for any document that you might email. You could do this each time, but it's much easier to set Open Office to save in Microsoft Word format by default. There are instructions here:
http://www.twistedeth...ve-as-doc-by-default/
Regarding Microsoft Office, you can download the beta version of Office 2010 for free from the Microsoft Office website. The beta version of Office 2010 will expire in October 2010, so you will have until then to make your mind up about purchasing Microsoft Office or using Open Office.
http://us2.office2010...lt.aspx?culture=en-US
Although it is a beta, I use it frequently and have had no problems at all.
Open Office does most of what Microsoft Office does. If you're adept at using Microsoft Office you will need a little time to work out where all the equivalent functions are. For the vast majority of documents, the compatibility of documents between the two programs will be seamless, but with complex layouts you will encounter instances where the document does not appear exactly as intended in the other program.