Adobe Acrobat PDF problem???

I use an accounting program, MYOB that lets me email Invoices directly to customers and I save copies of the emailed invoices in a folder in Outlook Express sent page.

I have discovered today that if I try to read a sent Invoice I get the following message;

This file does not have a Program associated with it for performing this action. Create an association in the Folder Options in Control Panel.

This has not always been the case and appears to have happend only in the past 5 - 6 days.

I have Adobe Acrobat 7xx installed on my computer.

Can someone point me in the right direction as I can't seem to find the right way to create an association, I'm sure it must be simple but it has me stumped.

Thanks in advance for any help.

 

Problem solved - I did a reinstall of Adobe Reader 7xx and problem gone.

Thanks to Halo for his interest.