If your idea is to have a dual OS setup with NTFS as the underlying format the answer is no.
You will need to reformat the HD back to the original GPT (GUID Partition table) partition with a Journaled HFS+ formatted volume for the Mac OS-X to sit on.
Using your OS install CD/DVD the system came with or a purchased Snow Leopard DVD you should be able to rebuild the HD back for OS-X. If you want to install Mountain Lion you will need to get back to Snow Leopard first then you can install it on top.
Once you get to the desired Mac OS-X you want you can then setup Boot Camp to setup a partition of Windows to run within. If you have that need.
As to protection - I would strongly recommend setting up two or more users on your system. The first user will be your Admin account (use any name you desire for this & password) This account will manage the Apps and general maintenance of your system. The next account is your every day user account (again pick a name & password your like here as well but different from the admin account) and you don't give it Admin privileges. To protect the data of this account you can also use file vault to protect this users files. In any case the Admin user still can't access the files of this user directly.
Doing the setup like this offers two distinct advantages: You can use the Admin account to delete the other account(s) if they get infected without having to loose everything and this users data can be doubly protected using file vault without using the full HD file fault protection (you can limit the vault to just a single or group of sub folders under the users account as well)
And of course - Don't forget your passwords!!!
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