Hi there
just new to the linux world. struggling to get through this in the shortest time. i have this problem disturbing me, don't know if any one can help.
i just did dual booting on my pc; on one partiton i install windows vista and on the other, i install centOS 5. windows partion can connect to the internet but the centOS 5 cannot. i even tried to change the speed on the network card from 1000mbps to 100mbps on the centos partition but it is refusing to change

you need not have to change the speed and most of the times the hardware auto-negotiates the speed.
if you say that you are not connected do you mean to say that the link is not up ?

may be from console you can login as root and paste us the output of
# ifconfig -a
this can help us find out issues with the ip addresses ...

i entered the follwing 2 command and got this:

[root@stanley ~]#ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:1F:299:18:64
inet addr:192.168.2.5 Bcast:192.168.2.15 Mask:255.255.255.240
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:6 errors:0 dropped:3144420496 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:759 (759.0 b) TX bytes:0 (0.0 b)
Interrupt:177 Base address:0x4000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:29 errors:0 dropped:0 overruns:0 frame:0
TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2606 (2.5 KiB) TX bytes:2606 (2.5 KiB)

sit0 Link encap:IPv6-in-IPv4
NOARP MTU:1480 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)


[root@stanley ~]# ethtool eth0
Settings for eth0:
Supported ports: [ FIBRE ]
Supported link modes: 1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: Not reported
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: FIBRE
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000033 (51)
Link detected: no

I think we need to see your network files contents, see Method 3 here: http://www.cyberciti.biz/faq/rhel-ce...configuration/