PP viewer isn't am email reader - unless somebody has sent you a PP presentation as an attachment.
Otherwise, yes, I would agree. A second-hand copy of such an application could end up as extremely iffy.
With some searching, I am sure you could find a legitimate copy of MS applications of 2003 vintage at a sensible price as most people are going for the 2007 versions now. Some auction sites sell legitimate versions - but as an OEM disc. This, of course, means no support documentation or assistance from MS - but there's a forum full of helpful folk here ;o)
Amazon have a deal through a private seller to provide MS Word 2003 with manual on disk. Cost with postage around £45.00 but does seem as you say a bit iffi and whether PP viewer is in the program I have to admit ignorance
Just require the program in order to read emails in that format.
If you buy MS Word 2003, it won't include PP viewer, but that can be downloaded from the MS site.
But I'm still unsure as to why you need it for emails. They usually are sent in a format that is readable by Outlook Express that is supplied as part of Windows. Unless the PP bit is being sent as an attachment to an email.
If you do go ahead with buying Word, check that the disc is a genuine and unused hologram one other registration will prove difficult.
You could 'go the whole hog' and look in ebay and get a complete MS Office 2003 (genuine) at a reasonable price - but do make sure that it is genuine and not a 'back up' version or similar.
I downloaded the free PowerPoint viewer on my home PC a year or two ago. From my experience, if I receive an email with a PP attachment and click on the attachment Windows says I don't have the program to open it. However saving the attachment to disc and clicking on it there does open with the viewer.