Ccleaner isn't an antivirus or antispyware. The part that I use, it helps clean out your temp internet files and other stuff that accumulates from web browsing.
The registry side cleans out left over files from when programs are installed or removed. Unless you know what you are doing with registry cleaners, best to leave that side alone as you can have things suddenly not working. That's why I use another trusted program and always have a restore point created first.