|You should be able to return it.|
One of the benefits of buying from a large company that they usually provide a way to return the system to OEM state. You may have to buy media for a nominal fee in some very limited cases but usually there is a way to make media or use a F key at boot to fix it.
The problem you have is that there is no control on the system.
Put a strong admin password on it and make only limited user accounts for the kids and yourself.
Consider using your home router's features also to limit junk.
Put on a good security suite also. At least ms security essentials.
Get a good hosts file too.
Uses and hard drive wiped out are not the deal here.
1/3 of highway deaths are caused by drunks. The rest are by people who can't drive any better than a drunk.