My wife has a PC, I use a Macintosh. Several years ago I got a registry cleanup program from Iolo that did a good job of straightening out registry issues. But then Iolo decided to go into the firewall, antivirus, antieverything business and bundled their registry cleanup utility with everything else. However, I was using another firewall/antivirus program and had no desire to switch, After all, I had a license valid for a year, the program worked fine, and I had three total installations, including one under Parallels on the Macintosh and one under VMWare on the PC (the license allows this). Iolo included the ability to detect third party antivirus/firewall programs, but their program failed to detect the antivirus/firewall program I was using. So I got bogus warnings, "No firewall detected. Antivirus not detected."
Meantime my wife's computer ran more and more slowly. Finally I got an email from Smith Micro announcing a registry cleaner called Checkit. I ordered it and installed it last night. I ran it and my wife is happy. The computer runs much faster now. It's a shame Iolo had to take a simple program and tie it together with other layers of code to do much more than I wanted done, but from initial experience, Checkit will do the job.