Windows Security..Firewall Off and Virus Protection Off..???

My Windows Security Centre says that my Firewall Off...Thats on my laptop..
It happened when I just restart my computer from un-installing a software I
dont want to have on my laptop.
After I restarted the computer....First thing it said my firewall is off...
It was on before I restarted my computer....
I tried to see if I can turn it on myself...But it says it can't...

How do you start it? Or make it to start...
I am not sure what firewall it is...All I know is when I installed windows
XP2....It already has one...

And the Virus Protection....It cant detect it.
I have the same anti virus software on my laptop and desktop. But my desktop
cant detect it...Even though they both have the same anti virus software...
I got AVG Free Edition. Updated as well.
My Laptop can detect it but my desktop can't.

How can I get my desktop to detect it?
It's also has Windows XP2 installed.
It detected the anti virus for a long time until one day I restarted the
computer and it wont detect right after a restart.

Oh and one last thing.....Not about the Windows Security centre.

My desktop wont connect to the internet from time to time...
Sometimes is does and sometimes it doesnt.
I got the desktop checked and see if there is anything wrong with the LAN
port where the cable is. They said nothing is wrong and they say it was the
cable.
I tried a few ways but the cable is working fine even though the desktop
wont connect to the internet.
When I try to use the re-pair connections.....It says it cant complete
re-pairing the connections because it cant Clear the DNS cache.

Is there anything which can make it connect to the internet fully?
And the Re-pair connection thing...About clearing that DNS cache thing.?