I still have an old Power PC machine and was wondering what the latest OS X build I can install on it?
10.5 Leopard is the last to support PowerPC as far as I know:
Snow leopard does support PowerPC applications, this function was dropped with Lion. I base this on one MacBook with Snow Leopard on it works fine with Microsoft Office X, Quake II (OS XVersion), Halo, Roxio Toast Lite 5.2.2.
However on my upgrade MacBook running Lion they are tomb stoned and when you try to run them the message you receive is PowerPcC no longer supported!