Uninstalling a program which uninstaller doesn't work

I recently accidentally deleted my appdata folder, so 50% of the programs went mad, including Aptana Studio. When I looked for the uninstaller, I started it, and the "Uninstall from here:" field was empty. I clicked uninstall anyway, but it did nothing. So basically now I can't uninstall it and make a fresh install. I can't delete the files manually because the settings will stay, and the fresh install will be loading them and not working either.

Aside from Ofir's answer, about the only other option you have are commercial registry cleaner utilities which find "abandoned" registry settings. These work with varying degrees of success and can potentially do as much harm as help, so make sure if you use one you take precautions such as manually backing up your registry first. Some of the more popular ones include: PC Tools Registry Mechanic and CCCleaner