network and tape drive problems

I once installed a tape drive on my box and eventually removed it(tape
drive) because it was damaging tapes. The problem now is that the server
keeps giving the following error: "Link down cable problem" 
And also it gives the following error message: " server using internal
transceiver,  full duplex mode at 100Mbps". 
I know this is caused by the network card and how can I set it to work at
half duplex or rather how can I solve this problem???

TIA
Blessing