Standard thoughts:
Virus - using a reputable AVS product up-to-date?
Spyware/Adware?
Proxy - you shouldn't have a proxy set in your Browser - Tools, Connections, LAN Settings
Some checks:
Go to a DOS prompt
type in:
Ping 192.168.1.1 (should get a response like)
C:\>ping 192.168.1.1
Pinging 192.168.1.1 with 32 bytes of data:
Reply from 192.168.1.1: bytes=32 time=1ms TTL=255
Reply from 192.168.1.1: bytes=32 time=1ms TTL=255
Reply from 192.168.1.1: bytes=32 time=1ms TTL=255
Reply from 192.168.1.1: bytes=32 time=159ms TTL=255
Ping statistics for 192.168.1.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 159ms, Average = 40ms
C:\>
TTL must be 255 for this check
Then try:
C:\>tracert 192.168.1.1
Tracing route to 192.168.1.1 over a maximum of 30 hops
1 1 ms 1 ms 1 ms 192.168.1.1
Trace complete.
C:\>
Should get exactly that
Next, try:
C:\>ping www.yahoo.com
Pinging www.yahoo-ht3.akadns.net [209.131.36.158] with 32 bytes of data:
Reply from 209.131.36.158: bytes=32 time=182ms TTL=54
Reply from 209.131.36.158: bytes=32 time=182ms TTL=54
Reply from 209.131.36.158: bytes=32 time=182ms TTL=53
Reply from 209.131.36.158: bytes=32 time=183ms TTL=53
Ping statistics for 209.131.36.158:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 182ms, Maximum = 183ms, Average = 182ms
C:\>
If you don't get something like this (ignore the exact numbers) then you have a problem.
If you get Lost = 4, then DNS is wrong, or you don't have internet connection.
Next try:
C:\>nslookup
DNS request timed out. (may happen, may not)
timeout was 2 seconds.(will happen if above line does)
Default Server: should be the name of your ISP's DNS
Address: (valid IP address - the value of your DNS - your ISP's)
>
If you don't get a valid IP address (perhaps with :53 on the end) then the value of DNS in your router is wrong, or your connection is broken, or you have a DNS setting in your Network Connections which is not the same as the one your router is supposed to have or your routers internal interface IP.
To check that, type:
C:\>ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . : (blank)
Wireless LAN adapter Wireless Network Connection:
Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 192.168.1.xxx
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
etc
Either Ethernet adapter Local Area Connection: or
Wireless LAN adapter Wireless Network Connection:
will have the IP address of your current connection - xxx cannot be 0, 1 or 255 - I choose to use 100
In more detail: (will give in part)
c:\ipconfig /all
Wireless LAN adapter Wireless Network Connection:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : (Brand Name) 802.11g Network Adapter
Physical Address. . . . . . . . . : 00-xx-xx-xx-xx-xx
DHCP Enabled. . . . . . . . . . . : No (my choice)
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 192.168.1.100(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : (my DNS 1)
(my DNS 2)
NetBIOS over Tcpip. . . . . . . . : Enabled
that's it - if you still don't get the internet, I'd be looking at connections.