If you are a Linux user and need to open PowerPoint presentations on this OS, then there are many different approaches that you can follow.
Using OpenOffice Impress to open a powerpoint Presentation on Linux
First of all, you can consider to open your powerpoint presentation online for example using services like SlideOnline that let you publish powerpoint and PDFs. However, if you need to edit powerpoint on Linux then the option is to use OpenOffice Impress (http://www.openoffice.org) or LibreOffice. Both are open source alternatives to powerpoint that you can use in Linux.
You should be aware in advance that opening a powerpoint presentation using OpenOffice or Libre Office may not give you the same results or look the same as opening in powerpoint, especially for Slideshow transitions, animations, working with powerpoint TEMPLATES or using custom graphics. However, you can get the presentation content and it is enough to review the presentation.
Related: Download OpenOffice Impress Templates
Extract a powerpoint Presentation to a Text File on Linux
If you just need to read the content inside a powerpoint, then you can use catdoc or catppt. It reads MS Word and MS powerpoint presentation file and puts its content on standard output. For example, you can follow the tips pointed here:
catppt filename.ppt > /tmp/presentation.txt
Open powerpoint on Linux using a Virtual Machine
Another open is to use PPTView (under wine or using a virtual environment) can be an option. You can install VirtualBox under Linux and then Win XP or Windows 7, Windows 8 to use powerpoint Viewer inside.