Network Adapter Problem.

After I turn on my computer for the first time today I wait for it to connect to my internet and see it has no success... It tells me that there is a problem with the Network adapter so I go through the troubleshooting guide and try all the things they suggest except updating the driver (because I can't get onto the internet).

I then plug my ethernet into it to try try update the Adapter but it says there's a problem with the Local Area Connection Adapter, the exact same as the Network one (I'm unsure if it's the same adapter for both).

So my only option left it is telling me is to replace the adapter but I really don't want to have to do this as my compter (27 inch iMac, Using Windows 7.) is quite new, we only got it at Christmas and cost a lot of money for us... Last night when I turned it off it was working fine... the only thing that would have changed anything was I had just installed the AVG 2011 trial but I'm unsure if that's the reason.

Please help me figure out if there's a way to fix this as I am totally lost with what to do...
Thanks.

• boot to Mac OS, see if you can connect to internet (to make sure the adapter/ network cables are physically still good in condition)
  
• are there other computers that can access internet using the same router/modem? If there are, try switch the cables (to make sure the problem is specifically at the adapter)
  
• in Device Manager
   Spoiler
  

  right click [computer]> Property> Device Manager
  
  locate your network adapter > Property > Driver, try Roll Back Driver there;
  or, insert your Mac OS installation Disk and re-install Boot Camp there.
  

- Yeah it seems the internet is connecting fine in Mac OS.

- I tried that when I put the ethernet cable into it, I swapped it with this current old computer I'm using to type and it didn't work.

- I did the Roll Back but it's still not connecting. I also put in my Mac Os disk but it gave no option to install boot camp in extra installs.

Thank you for helping, is there anything else you would suggest o.o?