I don't get an internet in my pc?

Hello all

I hv my pc at home, I was able to get an internet from the first time, now I'm not getting internet for about 4 dayz.

When I ping out, it tells me ' Request time out'

I hv checked the connection and it was ok
I hv tried to change the cable, nothing helped and the network card was perfect ok

pc specification:
hd 120 GB
RAM 512
Processor speed 2.8 MHz
Win Xp, SP 2

Please help