Here is a link to the previous discussion:
http://www.phpbuilder.com/forum/read.php3?num=2&id=108874&thread=108774
Here is how to use header() and readfile()
<?
header("Content-type: application/ms-word");
readile("prisoner-of-proprietary-format.doc");
?>
That's pretty much it.
Common MIME types include
application/vnd.ms-excel
application/msword
application/vnd.ms-access
application/vnd.ms-powerpoint
If the user is running Microsoft Windows 9x/ME/NT/etc and has all the Office suite installed and is using Internet Explorer, the documents should display in his/her browser. The rest of us are not going to be able to view most of that stuff.
The root problem is that the formats you mention are not open and are designed to keep you dependent on Microsoft's proprietary software.
The wvware library (www.wvware.com) has some ability to extract from Word files, but it is limited.