cant connect internet

EDIT:Computer just fixed itself??? I started up and it wasn't working and now suddenly it is. Oh well if you think I might have a virus or anything I should get rid of then please say so as that may be the problem.

Ok yesterday when I was using the internet my computer restarted itself. I thought it was due to heat so I rested it then came back on and the internet doesn't work. It says network cable is unplugged even though it isn't and the cable is working as I tested that. Also when I rebooted after it restarted itself it said the computer had a system error.

Since then I have looked around and tried things like pinging localhost, removing NIC card and cleaning it, checking network cord, restarting modem, disabling NIC in device manager and restarting computer and then enabling NIC again, restarted several times and that is all I can remember for now. I really would like to connect to internet again so any help is greatly appreciated!

[edit]
I also disabled some bios settings which allowed computer to boot due to LAN and some others because my computer was at one point booting on its own which it has never done before (VIRUS MAYBE). I also reset IP settings with command promt and scanned computer with spyware search and destroy and with AdAware. I have also tried disabling firewalls however this didn't work