Advanced Edit error message when editing Outlook Signatures.

I am running Microsoft Office 2003 on Windows Vista Basic Home version. When
trying to add, or edit my signatures in Outlook, I utilize the "Advanced
Edit" feature. It worked well when using a different PC, running Office 2003
on an XP-based system.

When adding signatures for e-mail, I am used to clicking on, when in Outlook:

Tools
Options
Mail Format
Signatures
Edit
Advanced Edit

Then I receive a box with the following message:

"this will launch an editor that is not part of Microsoft Office Outlook.
Do you want to continue?" (I click "yes")

At this point I receive the following Microsoft Office Outlook error message:

"Could not find an editor for H(.) files"

Any suggestions as to why I am receiving this error message?