Ok lets try a few things here and see if they get you up and running.
First off lets consider doing a total wipe of your drive and a XP reinstall.
Now is a good time to recheck all power connections to the motherboard, drives and video card. I am assuming you know not to use both the SATA power cable and the ATA power connector at the same time.
Did you drive come with a setup disk? If yes there should be a format utility in the disk to allow you to do an intial format and enable the entire size of your hard drive.
Follow this link to get the software:http://www.seagate.com/support/disc/...s/discwiz.html
copy to a cd and change the bios to boot to the cd and run the utility.
Check your motherboard instructions on how to run the motherboard with one video card. You may have to either make a BIOS change or a jumper change. Get that fixed before you install the OS.
Now lets install windows XP. Copy the SATA drivers to a floppy and put it in your system. When prompted for the SATA drivers hit the F6 key and load the SATA drivers. Now follw the on screen prompts to finish up.
Load and run windows xp, but do not activate it just yet.. Once you have XP installed go to the XP update site and install you updates and service packs. When that is done and the firewall is set up activate windows.
Now reboot and change your boot order to the hard drive.
When you are at the boot screen install the CD that came with the motherboard. Either select the autorun option or start from the top menu of drivers and go down the list until all of the motherboard drivers are installed.
Be prepared for multiple reboots.
Now at this time install the video drivers from the install disk that came with the card.
This should get you up and running in no time. If you get stuck PM me and I will do what I can to help you.