D-Link ADSL2/2+ Router dsl-524T

please can someone help me, my computer has been troubling me since xmas with problems after problems, but i managed to find a soloution to all of them apart from this one.
i've just bought a new Dlink DSL-524T ADSL2/2+ router. i put the cd in, hooked up the power supply, connected the adsl telephone line[which works because that's what i'm using on my usb adsl modem now], and connected the ethernet cable to the back of the router and to the only ethernet port on my pc, which isn't in one of the pci slots.
When i used the installation software, everything was goin swimmingly until the setup began checking the 'physical connectivity status' of my device. an error message appeared saying:
"Modem not detected! Please check the following:
1.The power adapter is connected to your modem and electrical outlet
2.Your modems ethernet cable is properly connected to your computer
3.Network card is properly installed on your computer."

The modem tslf seems to be working properly, all the lights are on or flashing as they are supposed to be. however, the ethernet port on my pc glows orange when the cable is connected, i'm unsure but i always thought it was meant to be green. the only solution i can think of is to buy a d-link network card for about 15 gold, and hopefully that would work. also, the modem has no drivers which i thought was odd because my friend asked me if i had installed them, but there are none.
my pc is a dell dimension 2400 by the way, and i have tiscali bband. my modem can be found at both of these links:
http://www.eclipsecomputers.com/product.aspx?code=FMD-DSL524T
http://www.dlink.co.uk/?go=gNTyP9CgrdFOIC4AStFCF834mptYKO9ZTdvhLPG3yV3oVo9/hKltbNlwaaFp6DQoHDrryC9K944IBt7n

apologies for the longness of this, just wanted to make sure i got everything mentioned. thankyou for any help.