Nothing is detected as in neither hard drive are detected? OR the new drive simply insnt showing up in windows?
if the second is the case then you have to partition and format the drive before windows is going to see it. if you are using XP then go to adminsitrative tools\computer management\disk management. the drive should show up there, right click the drive and chose partition. then format it.
if your bios is set to raid then it is looking for a raid setup on boot, and you dont have one. uless you are planning to set up a raid array ( you will have to reinstall windows to do this) try disabling the raid in the bios.