USB to CAT 5; Microsoft 6to4 Adapter ---PLEASE HELP!!!

Ok, how can I sum up this issue...

Basics:
(5 mths old) Compact Presario - Windows Vista
Internet- Comcast broadband
-trying to hook up router but can not use the cat 5 plug on the PC

ok, my internet works fine when I have the line coming from the modem to the PC (via USB)

I just bought a router and have to hook it up using a cat 5 line. Ok, no problem, my PC has both...

So, after going through the installation steps, changing the hook up to a cat 5, my main PC does not get internet...

So to check my cards to ensure, I went to device manager and found that adapter everyone speaks of "Microsoft 6to4 Adapter" with the yellow exclamation next to it...I tried everything, update driver, ipconfig (release and renew), resetting everything, unplugging, even searched Google... So I said what the heck and deleted the adapter... when I did this the back of the PC (where the cat 5 goes) the light was no longer lit up.

First question... is this the reason I can not get internet through the router (this non-working adapter)?

Second... could it be the NIC card for the cat 5? The pc is only 5 months old, I can not imagine it being broke, but I guess things happen (than again if this was the case why would he light next to the plug light up when I plug in the wire?)

Someone please help!!!

If you were using an USB ethernet adaptor it's possible the onboard ethernet network card was disabled via the BIOS.

Check to see if your ethernet card is firstly working and windows device manager recognises it and has drivers installed for it and then check the bios.

I did check the device manager and all adapters except for the Microsoft 6to4 Adapter was working. Do I even need the 6to4? How do I check the Bios?

Thanks for your help...