dhcp problem on dell laptop

我有个dell inspiron 8500, nic 是broadcom 4401 on board nic. 我用wireless 没有问题。但我用cable connect to router，nic doesn't talk to dhcp. i always get "dhcp server error, dhcp request has timed out". 我的desktop连到router没有问题，我用cable connect lap to adsl modem，也没有问题。但就是不能从laptop连到router with dhcp. 我也试着set internal ip statically, it doesn't work either.请教各位大侠，有没有甚末好办法，先谢过了