I have a new Computer that comes with Windows Vista. My e-mail recipients
are not able to open my attachments because they have an older version of
Windows.
No, not so. What version of Windows you have or they have is
irrelevant.
You didn't say what kind of attachments these are, but I'll take a
guess. Have you created them in Office 2007?
If so, the problem is that you are using Office 2007, and they are
using an older version of Office. Office 2007, by default, produces
files in a new format--for example, Word files are .docx rather than
the old .doc.
If that's the problem, just save the file in the old .doc format.
Instead of doing "Save," just do "Save as," and change the type to
..doc. For Excel, save it .xls, instead of .xlxs,
For longer-term compatibility, your recipients may want to install the
free downloadable Microsoft patches to their office versions that
permit them to read the new formats.