Tbh, I wouldnt let any little kids (i.e. Under 16) on my computer. I would double-password it at the BIOS level and OS level, and just in case, I would limit all the accounts and make a backup of my system with Symantec's Award Winning
Norton Ghost 12.0, which is very easy to use. Anyway, be prepared to format if you don't get it figured out and locked down well...they pretty much click all those ad's and install stuff like SmileyCentral and Games with Built in Trojans, etc...
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