1. Restore OS X Snow Leopard;
2. Partition your hard drive or add an external hard drive and install Snow Leopard into it and use the "dual-boot" method to choose between Microsoft Office 2004 or Lion/Mt. Lion;
3. Upgrade your software to Microsoft Office 2008 or 2011, or find alternative software that will open, modify and save your data files;
3. Install Snow Leopard (with Rosetta) into Parallels:
[click on image to enlarge]
Full Snow Leopard installation instructions here:
NOTE: STEP ONE of the instructions must currently be completed on a Snow Leopard or Lion Mac and the resulting modified Snow Leopard.cdr install file can then be moved over to your Mountain Lion Mac for completion of the remaining steps. A recent poster has offered a solution for Mountain Lion users that do not have access to Snow Leopard or Lion Macs.
NOTE 2: Computer games with complex, 3D or fast motion graphics make not work well or at all in virtualization.