PowerPC applications not supported when I downloaded LION?

Sorry, but Lion does not support Power PC apps.

Read here > Lion upgrade questions and answers: Apple Support Communities

If you ran PowerPC apps on Snow Leopard an alternative is to downgrade.

How do I uninstall Lion: Apple Support Communities

You can use Rosetta on Snow Leopard for Power PC apps > Mac OS X 10.6 Help: If you need to install Rosetta

Dove in before checking the waters. There are three things that you could do now. Update you apps, revert back to SL or three partition your drive and have both OSes on your mac. Problem with this action, it can get quite confusing on how to handle your mail, calendar ect. as you can have only one running at a time. Should you decide to go this route, use Lion as your goto system and only revert back to SN if you must to run PowerPC apps.

Yeah, Jim_B, you did dive in too early. The easiest way around it is to use BootCamp to create a partition in Lion and install Snow Leopard on it. It means you will have to restart between discs, but at least you will have your apps. I did it the other way around by putting Lion on a partition. Glad I did too.

Why use bootcamp when you could use Disk Utility to partition the drive. Much easier.

Jim_B,

If you use BootCamp you don't have to erase the hard drive and you can keep the other OS. I went that route because I was apprehensive about installing Lion as my main OS and, as it turned, it was a wise choice.