Open Office will open files saved in the Word '97-2003 format. This can be done one of two ways.
One is the long way, that is open Open Office Writer and then click on File, Open and then use the search function in that box to highlight the file and click on Open.

The above image shows a file I created in Office 2000 on another machine some time back. If opened just fine.
The short cut method depends on how Open Office was set up initially. For those who have not yet installed Open Office and do not plan to use Microsoft Office the following image is important. Early in the install process the following dialog box is displayed, and basically what it is asking is if you want to use Open Office as the default to open the following MS Office file types. Checking them will enable you to simply click on the file and it will open if in Open Office.

If you have not done this, you can still after the fact direct Open Office to by default open MS Office files. The following is for Vista, but if there is somone who needs this for XP, please ask in a post. It is basically the file association where you associate a file extension with a program and that program is automatically opened when the file is double clicked.
The file I have selected is the same Word document used in the above example. It sits on my desktop, and by placing the cursor on the file icon and right clicking, a menu box opens. About a third of the way down is an item called Open With and it has a little arrow to the right. Placing the cursor on that menu item then opens a secondary menu box that has three items. Microsoft Word (2007 in this case) something called swriter (which is the file name for Open Office Writer and then a choice for default.

Selecting either of the document generators (Word or Writer) will only be effective for this particular document this time. If you select the option of default, the following option box opens.
You select the program you want and highlight it, make sure the check box for Always use the selected program to open this kind of file is checked, click ok and the file will open. In the future, double clicking this file type will always be opened by the one you selected.
Since I have Office 2007 on this machine, I have left the default for .doc as Office, but can still open a .doc file anytime in OO Writer.
Note that the default file saving format of OO Writer is .odt, but that while OO Writer will open a Word .doc, Word is unable to open a OO Writer .odt file. So if you are exchanging files with someone, unless you know they have OO Writer, you should use .doc to save the file. Clicking on Save As opens the listing of file types.