Opening old Power Point files

I have a large number of Power Point files that were created in 1995, 1996, 1997, and later using then current versions of Power Point (3.0 and earlier versions I think they were ... and since these were federal governement computers the operating system was probably whatever was before Windows 95).  I upgraded to Windows Vista 64 anad a new computer in August 2009, with Office 2007 and recently needed to open a Power Point presentation from 1997 and use it the historical data in a new presentation.  My computer wouldn't open the file and said that my current Power Point doesn't support earlier versions.  I then tried to open the 1997 file one of my other computers that has Windows XP and Office 2003.  The file wouldn't open on that computer either giving a similar message.  I also have an antique computer with Windows 98 that isn't very reliable, some of these old Power Point files can open on that computer with a little animation of pages flying through the air saying it is updating from an older version of Power Point.  I have hundreds of old Power Point files and some of them still have relevant historical information that I need to use occasionally without having to remember the details of what I put on them then.  How can I open these old Power Point files on my new computer?