I could be wrong but I'm not sure CCleaner takes out the last thirty days of History, including Cookies. In any event, a professional - if sufficiently bothered and curious - would use undeleting software to get it all back. Piriform,. the CCleaner people also develop Recuva for just that purpose.
To be more certain, bin it all using CCleaner then defragment the disk and run CCleaner again, this time ticking Wipe Free Space. It takes time but it's more thorough. Untick it afterwards otherwise it does it every time.