Bob runs a program called "Evidence Eliminator" which wipes and overwrites his hard drive. It erases everything, though. Is there a better option?
Leo says why not just use private browsing mode in his browser? (Firefox and I.E. - Private Browsing, Chrome - InCognito). Each session is private with nothing saved. Remember that while he can wipe out his local footprint, his ISP knows everywhere he goes. Those programs, such as Evidence Eliminator, are red flags too.
There are a number of alternatives to Evidence Eliminator, since it went out of business: