PowerPoint Viewer 2007

My wife uses a desktop PC with Office 2003, including PowerPoint 2003. So far all PowerPoint files sent as email attachments open & run OK.

I use a older laptop with Works + Word, and it doesn't have PowerPoint installed. Both computers use XP Home + SP2, fully patched and all applicable Office updates & patches as well, including the update for Word 2007 DOCX files. Both computers run IE7 and OE6, again fully patched.

On the laptop I have been using PowerPoint Viewer 97 satisfactorily until recently when several files (*.pps) wouldn't run. Often the first screen would open but nothing else except for the last page.

I have downloaded and installed PowerPoint Viewer 2007, thinking that this would open all files from 97 onwards. But it is no better at opening these problem files than PP Viewer 97.

Additionally, since installing PP Viewer 2007, I cannot open any PP attachment in Outlook Express 6, something I used to do all the time. When I try this, even with PP files that used to run, the file now opens in Notepad, not PP Viewer 2007.

I have checked the file associations in Folder Options, and PPS as well as PPT files are set to open with PP, but the only way that I can open these files now is to save the attachment to hard disk and then the file association will open PP Viewer 2007. At this point the files that opened OK in PP Viewer 97 still open OK, but the problem ones just won't open beyond the first & last pages.

I have uninstalled and re-installed PP Viewer 2007 but have now run out of ideas. I have just installed Service Pack 1 for PP Viewer 2007, but it did not fix the problem.

Any help would be greatly appreciated.