I make no claim to being a legal expert. However, it appears that the word
"Excel" is not trademarked; see
http://www.microsoft.com/library/toolbar/3.0/trademarks/en-us.mspx
However, when I approached Microsoft many years ago prior to publishing my
first book they wanted me to use the phase "Microsoft Excel" everywhere. We
agreed I would do that the first time in each chapter. Note the Microsoft is
registered. So you use Microsoft® Excel.
