Some can be a scam type, for example, will scan , then to fix/repair, want you to pay for it. The windows defrag, while slow is really all that is needed, however , some 3rd party free ones i have checked out and used once in a while is called Defraggler, was at the Piroform site , it wanted to install a toolbar, which is ask toolbar, which i used another program to get rid of that. That program is called PC-decrapifier.. fitting enough.. I guess what i am saying, you really do not need to use 3rd party applications to assist in the windows programs, the only one i really like is revo-uninstaller, but, that one has to be used with a careful eye , specially if you use the advanced mode. In the big picture of things. a few straggler files will not harm you OS> so. choose wisely . Hope this helped you in some small way .