Prevent history deletion on Google Chrome
There is now a way to do this using preferences. It's not very well documented but here is the chromium ticket that adds it. Add the following to your chrome preferences file which located here.
"history": {
"deleting_enabled": false
},
If you are REALLY worried about this, you may as well install a commercial keylogger in the computer! Most of the time, this is illegal to do but i think this is really good way to get hold of the browsing habits. The extremely bad side of this suggestion is that you get all the keystrokes = password/credit card information etc which i believe is not what you want :) So a configurable keylogger which will only track the web browsing perhaps :)
Or another perfect way of doing this is configuring OpenDNS to be used with the computer. Not only you can block unwanted (pornography/social networking/drugs/time wasters +much more), the free version (which is more than adequate) will give you two-week insight to all the networking activities (which sites were visited/which blocked sites were visited etc). To add to the effect, you can show your own message + picture when a site is being blocked :D
Hope this helps :)