slow network with collisions in hub

i have domain with windows 2000 server and windows nt client machines. i have setup the network with one hub and one switch. and combined hub and a switch with a uplink in the hub to the switch normal port with a straight cable. server ip is 1.1.1.1 with subnet mask 255.0.0.0. the problem is this that the network is slow and hub shows the collision when pick some software for installation from the server or some other client machine. i can access sometimes other computer very slow and even sometimes it shows a error that the network not found. i am really upset and exaust . plz help me out to tell me the right and quick way.

i will be grateful to u.

regards