Doesn't it do the same things that you can do manually? Like start a Disk Cleanup and Defrag? (I could be wrong)
Do you know what Operating System you have? Windows 7? Windows 8?
This is how to defrag: http://youtu.be/RnbfIZlFnaE
I think the Disk Cleanup option would be somewhere near there, too.
Eagles has a good point. PCmatic is just a software that does the same as disk cleanup and they may even want money after its done. Your best bet is to just have a good antivirus like Microsoft security essentials (free from Microsoft) and run the disk defrag yourself. It may take forever but its the safest.
DO NOT DO IT
I use ccleaner
its not really free.. someone told me its a free download but you have to pay for the cleaning features.. its pointless.
no prob, try ccleaner , you can download for free at piriform.com/ccleaner