It's an autocorrect option, you can disable the behavior there. Also, at least in 2000, when you right click on the cell one of the options is "remove hyperlink".

A hyperlink is an HTML element that provides a link to a different location. A person can create a hyperlink to link to different documents, emails, and Websites. In Microsoft Excel, PowerPoint and ...

Are hyperlinks not opening or working in your Excel workbooks? In Excel, hyperlinks are used to open specific documents, files, folders, or web addresses saved on a network server, intranet, or web.

How to use hyperlinks to move quickly between sheets in Microsoft Excel Your email has been sent Why Snapdragon is Built for the Next Enterprise Frontier PCs Powered by Snapdragon vs. Legacy Devices: ...