Hi,
not to sound pessimistic, but there are a lot of variables to take into account in setting up secure networks. Yes, the software you mentionned is a great start, but what is the most important aspect, IMHO, is to know how to set them up properly and to know how to diagnose/interpret the information given by these tools.

For instance, you have to know how to interpret the 'threat' messages given by a firewall: some warnings may simply be generated by your online activity while other warnings that may appear somewhat trivial may be signs of an attack.

Furthermore, the firewall router that you mentionned will not do much unless, as expected, it is correctly configured. You may want to enable MAC filtering within the router. Furthermore, blocking ports that are not used by your programs (or your dad's, in this case) within router may be a wise decision.

Another pointer would be to check which services are running on your computer: some services are asking simply 'asking' to get used and abused by hackers so it may be wise to go over them with your father to determine what is needed and what is superfluous. This can be done by going Start->Run->msconfig->services.

There are many, many more things such as logging,password complexity of your accounts, etc, etc, that I believe you should check before declaring your network 'secure' (btw, there is no such thing as a 100% secure network: you should be honest with your dad and tell him that).

You may want to check the following resources for additional help:
http://csrc.nist.gov/publications/nistpubs/index.html (NIST publications)
http://www.nsa.gov/snac/ (NSA).

all the best,
banshee