if i use a router to connect two computers to the internet using a braodband connection, will the router block out everything harmful such as viruses, hackers, spyware, adware etc. In other words do i still need the firewall and antivirus programs still on my computer?
Depends if you have a firewall built into the router. Even then, this won't block spyware, viruses or hackers. It will thwart a hacker's attempts, that's all.
For maximum security, I'd recommend leaving firewalls on the two computers and their respective virus protection and spyware removal / detection tools.
If you removed the firewalls on the computers, if one became compromised then the other would be easily accessible.
the NAT part of the router often acts as a firewall, but still use software firewalls on your computers as a backup. It's better to be safe than sorry.
and as OBonio says, it wont protect you from virii, spyware etc.