Choose About this Mac from the Apple menu, check if the computer has at least a Core 2 Duo(not Core Duo) or better CPU with at least 2GB of RAM, and if it does, click here and order a download code for Lion 10.7.
Mac OS X 10.7 and newer don't support PowerPC programs such as Microsoft Office 2004.
Check to make sure your applications are compatible. PowerPC applications are no longer supported.You can share Mail, Calendars, and Contacts running Snow Leopard. Based on my experience, I don't recommend syncing Contacts - created a lot of problems with duplicates.