Are they compatible? I just ran a Cat6 from Modem to 24 port switch and Cat5e from switch to 24 LAN cards.?

what kind of switch is it?

The only lights that will be on on a switch are the ports with a device plugged into them. So you can have all 24 ports on your switch with cat5e in them but only 2 computers hooked up to two ports the port they ar connected to are the only ones that are going to be active.

No matter what nic and switch you have they are compatible they all run 802.3 protocol.

You also have to remember that when you hook up to a switch then to say a cable modem you are splitting the bandwidth between all the computers connected to the switch. Your bandwidth and network may not be able to handle 24 computers of traffic at the same time so you are getting so many collisions that it is just crashing the network.

You need to start from the bottom and, work your way up i.e. Check the server first to make it is wired correctly. Then, you need to have entirely Cat6 or, Cat5e. You can't have both.

Mixing the two is, sort of like, mixing ketchup and, mayonnaise. It will make you sick.

The same goes for the LAN cards. They all need to be the same. Otherwise you will compatibility issues there, two.