Free PowerPoint Download

If you just want to open a PowerPoint file instead of editing it, you can download a
PowerPoint Viewer 2007 (free):
http://download.microsoft.com/download/f/5/a/f5a3df76-d856-4a61-a6bd-722f52a5be26/PowerPointViewer.exe

If you want to edit a PowerPoint file,you can download a
Office 2010 Beta (free for half a year or so):
http://www.microsoft.com/office/2010/en/home-business-edition/default.aspx

Office Web Apps: (Free) (A Window Live ID is needed)
http://office.microsoft.com/en-us/web-apps/redir/XT101857758.aspx

Office 2010 free trial:
Offce Home and Business 2010
http://office.microsoft.com/en-us/try/redir/XT101852693.aspx
Office Home and Student 2010
http://office.microsoft.com/en-us/try/redir/XT101852692.aspx
Office Professional 2010
http://office.microsoft.com/en-us/try/redir/XT101852694.aspx


Or you can download a
PowerPoint 2007 (free trail for 60 days)
http://us20.trymicrosoftoffice.com/product.aspx?re_ms=oo&family=officepro&rps=1&culture=en-US

If you want to open or edit a PowerPoint 2007 file on PowerPoint XP,PowerPoint 2003 or PowerPoint 2000, you can install the plugin:
Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint File Formats(free):
http://download.microsoft.com/download/9/2/2/9222D67F-7630-4F49-BD26-476B51517FC1/FileFormatConverters.exe

Besides, you can use other solutions:

Solution 1:
Kingsoft office 2009(free)
Open, Save and Create any kind of Office document, Spreadsheet or PowerPoint Presentation, without any difference in style and layout - Yup.

KSO09 is not based on OpenOffice, It's the quickest, smallest, 100% Microsoft™ compatible office system for Windows.
http://www.kingsoftresearch.com/downloads/setup_US_1033_6.3.0.1736_Professional_full.exe

Solution 2:
OpenOffice(free): http://www.openoffice.org/
OpenOffice.org 3 is the leading open-source office software suite for word processing, spreadsheets, presentations, graphics, databases and more. It is available in many languages and works on all common computers. It stores all your data in an international open standard format and can also read and write files from other common office software packages. It can be downloaded and used completely free of charge for any purpose.

Solution 3:
Google Docs(free): http://docs.google.com/

Create basic documents from scratch or start from a template.
You can easily do all the basics, including making bulleted lists, sorting by columns, adding tables, images, comments, formulas, changing fonts and more. And it's free.

Upload your existing files.
Google Docs accepts most popular file formats, including DOC, XLS, ODT, ODS, RTF, CSV, PPT, etc. So go ahead and upload your existing files.

Familiar desktop feel makes editing a breeze.
Just click the toolbar buttons to bold, underline, indent, change font or number format, change cell background color and so on.