We have never issued a warning on the use of any freeware application as we only post applications that have been tested on a clean OS installation; however, we ran across this one from CIL Software that not only crashed a few features, but also caused significant damage to required Windows files when using the "clean" feature.
The software in question is
Complete System Tuneup
We tested the program on a clean installation of Win 7 x86, x64 several times with reproducable errors. We did contact the author of the software who was not interested in hearing the faults of the software.
We will be creating a new section for problematic freeware, but in the meantime, this one is a "Do Not Use".