Help with router access

[Den]

Just received this email from my son, anyone with any ideas. If this gets in depth I will ask him to log on here

I have a D-Link DSL2640R Wireless Router, with 4 desktop computer linked by LAN leads. TWO computers work fine, no problems at all, TWO computers don't. The same two computers also don't work with wireless 'dongles' but two other laptops work fine on wireless. I have tried accessing the router and making sure all settings are correct...Ive set all computers up to exactly the same settings, and have also tried static IP addresses, and also tried different LAN leads, etc.... seem to have tried everything, inc looking up on other forums where people have had similar problems, all seem to have been solved using different methods, but no methods have worked on these two things that are soon to be flying out of the window...HELP!

[DorsetBoy]

What happens if the ports/leads are swapped around ?

[Steve]

If the router DHCP server is on and the computers network cards are set the same it should work. But he's tried that. Are the computers not working getting an NAT IP address or just a local one? Any software firewalls installed?