Try http://www.sandboxie.com/ you can keep using it for free, just have to wait a few secs, it will encapsulate your browser in a sandbox, you can also right click on an exe file > Run Sandboxed.
Any file that you download will ask if you want to recover it.
Any spyware or tools bars etc.. will stay in the sandbox, you can then delete the sandbox regularly.

Avira Free is ok just don't upgrade when it recommends.

How It Works

Sandboxie runs your programs in an isolated space which prevents them from making permanent changes to other programs and data in your computer.




The red arrows indicate changes flowing from a running program into your computer. The box labeled Hard disk (no sandbox) shows changes by a program running normally. The box labeled Hard disk (with sandbox) shows changes by a program running under Sandboxie. The animation illustrates that Sandboxie is able to intercept the changes and isolate them within a sandbox, depicted as a yellow rectangle. It also illustrates that grouping the changes together makes it easy to delete all of them at once.