Link opening problem

[L5wolvesf]

Hi,

I keep notes and other info on Word (2000) files. Part of those notes etc are links to websites. Until recently all I had to do was click on a link and Explorer would open to the site/page. Recently all I get for any link is an error message which says;
Unable to open <website>. No program is registered to open this file.
Explorer works OK, and so does Word, other than this and that is has been getting slower. How do I get back to the good ole ways?

Thank you,
L