CC Cleaner is a free download and very well respected. However, a word of advice. Don't be tempted to run registry scans too often as there is a danger of deleting important registry files. If you do use this function make sure that you accept the option to back up registry files. Open a folder for this in My Documents and name each back up with the date. Have a read of this article which also has a link to the download.
In addition, should you suspect a problem with malware free Malwarebytes is an excellent programme. Read this article for information and a link to the download.