Office 2004 Applications Won't Work in Lion
You must have Office 2004 which is a PPC-only suite and will not work in Lion. You need to upgrade to Office 2011 - Mactopia - or you can try the freeware suite, Libre Office, that is functionally similar to Office 2007 for Windows except it works on Lion.
You may want to consider as well:
These two suites are similar to Libre Office but not as current or as well-supported:
And, then there is Apple's iWork suite:
Pages - word processing and layout
Keynote - presentation
Numbers - spreadsheet
Each can open and save Office compatible files. They may be purchased separately via the Mac App Store for $19.99 each.
(Access to the Mac App Store requires Snow Leopard 10.6.6 or higher and an Apple ID.)