Got to be honest I've not heard of any version of Quark Xpress available as a free download. I've got the Mac version.
Was wondering though why you've got a document created in a programme that you haven't got installed on your pc. Like anything else, Microsoft Word or Works for example, you need the application to open it.
If you decide you have to buy Quark Xpress, try this place
http://www.lpstore.ws/index.php?target=search& fl=Q
It'll cost you about �20 compared to about �300 from other outlets. It's available as a download once you've paid and I can recommend the site - I've bought from them several times and at that kind of price you can see why!
By the way. The link is for the page with the PC version. I think there is a Mac version also by clicking on the Mac link in the alphabet list at top left hand corner of the site.