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.)
Before Mac switched to Intel processors they used Power PC processors from 1994 to 2005. Power PC 601 through 604, G3, G4 and G5. Applications written for the Power PC processors need the application called Rosetta to run on Intel processors. This was part of the Operating System in 10.4 and 10.5 but was an optional install in 10.6. With 10.7 Lion Apple dropped all support for Power PC applications.