hi
Using ethernet cables throughout 'should' give a hassle free installation.
Start with power off to all the components.
The modem should connect to the 'WAN' port & the individual PCs to the 'LAN' ports on the router.
Working with the default router settings (reset to factory defaults, if necessary) should mean that once everything is connected then switching on in the order modem, router, PC1 & PC2 should enable the connection. The important thing is to allow enough time for each component to fully initialise before switching on the next one - usually at least 30 seconds.
If it still doesn't work then the possibilities may include a faulty cable (or a crossover cable where a patch cable is required), or a faulty network card (does it show as enabled in device manager?)