My sis has been chatting with strangers online and my parents have forbade her to do so but she's being a stupid brat so now I have to lock up all the messengers.

However she's now onto web messengers and I've changed the HOSTS file so that she cant access these sites. But she somehow she found out about this. I'm using File & Folder Protector but it doesnt allow me to lock/protect system files so is there any alternative and small programs that could do the task?

Wow thanks a lot. That's actually the first link on google if I search "lock hosts file". Guess I'm kind of an idiot.