Here is the one of the most required software for Apple PowerPC Macs: Virtual PC.
Virtual PC for Mac lets you run Microsoft Windows applications, access Windows networks, use Windows-only Internet applications, and share files with Windows-based colleagues. Virtual PC for Mac employs standard Mac controls and commands. It gives you the flexibility to work across platforms side by side without changing your Mac OS, software or files. Say goodbye to compatibility issues. Virtual PC for Mac lets you have the best of both worlds.
Windows Virtual PC (formerly Microsoft Virtual PC and Connectix Virtual PC) is a virtualization program for Microsoft Windows operating systems, and an emulation program for Mac OS X on PowerPC-based systems. The software was originally developed by Connectix, and was subsequently acquired by Microsoft. In July 2006 Microsoft released the Windows-hosted version as a free product. In August 2006 Microsoft announced the Macintosh-hosted version would not be ported to Intel-based Macintosh computers, effectively discontinuing the product as PowerPC-based Macintosh computers are no longer manufactured. The newest release, Windows Virtual PC is available only for Windows 7 hosts.
Virtual PC virtualizes a standard PC and its associated hardware. Supported Windows operating systems can run inside Virtual PC. Other operating systems like Linux may run, but are not officially supported.
Virtual PC for Mac 7.0.3
This update fixes a vulnerability that an attacker can use to overwrite the contents of your computer’s memory with malicious code. This update is recommended for all users who are using Virtual PC for Mac 7.0, 7.0.1, and 7.0.2.