In addtion to what Kendor says Reinstall the Router And you'll be remaking the Password too
Have it connected to the Equipment which is giving you trouble and it might recognise it this time ?
Before you do this Disable your Windows Firewall
and Your software firewall and go ahead with the install Now Try going online? Any Luck?
If the answer is yes renable your software firewall ONLY
You'll find in the Security Center that It been given a Green "light" The Windows Firewall
will Help out still...But won't conflict
and messages will be generated by the Software Firewall
It does also say in the Security Center that 2 firewalls is Not a good Idea ...Hence You will get a Block or something

Bottom Line Which all Computer Forums say to a Man
DO NOT RELY ON THE WINDOWS FIREWALL ALONE (it is weak) The Router also has a built-in Firewall and the Password/Serial Number generated Protects the Network ONLY!
Therefore all the Network needs an Individual Software firewall setup to protect it both from itself and the Outside world
PS If you cannot afford a Commercial version
There are some Free Firewalls available
I hear
Comodo is the best of the Current crop Take a browse of several more at
http://filehippo.com/software/firewalls/ All bar 1 are small download sizes
(Comodo weighs in @ 9 MB)