個Router do 上唔到網既....

Do the following steps:
1. make sure those 2 PCs are connected to the router, then turn off the router first.
2. wait for 5 seconds, then turn off your modem.
3, wait for another 5 seconds and turn your modem back on
4, wait for all solid green lights on the modem, then on your router.
Check both PC to see if internet is now connected

If the above method does not work.... It could be the router firmware...
What is the router model? There might be a latest firmware version for your router causing the trouble. If so, go to the website and download the latest firmware.

Hope this helps

By the way, are you connecting those 2 PCs wirelessly?