|"Before I reformatted my computer this DVI monitor worked fine."|
You should have mentioned that in your first post. That's a whole different situation, assuming you didn't still have the VGA connected monitor plugged in when the DVI monitor worked before (if you did still have the VGA connected monitor plugged in at that time, of course the DVI monitor would have worked fine).
Did you load the main chipset drivers?
Whenever you load Windows from a regular Windows CD (or DVD) from scratch, after Setup is finished you must load the drivers for the mboard, particularly the main chipset drivers, in order for Windows to have the proper drivers for and information about your mboard hardware, including it's AGP or PCI-E, ACPI, and hard drive controller support. If you have a generic system and have the CD that came with the mboard, all the necessary drivers are on it. If you load drivers from the web, brand name system builders and mboard makers often DO NOT have the main chipset drivers listed in the downloads for your model - in that case you must go to the maker of the main chipset's web site, get the drivers, and load them.
One of the things in the main chipset drivers are the drivers and/or information Windows needs to properly recognize the mboard chipset's enhanced video (specifically, GART) support.
Your video card will work fine in plain VGA mode but when you load specific drivers for it, in this case AGP drivers, the card will not work properly if Windows doesn't have the proper drivers and/or that proper info.
The other thing you must do is to load the proper drivers and associated applications for the video card, the right way.
XP has built in support and drivers for 9800 series cards, but the drivers on the CD are newer, or the ones you get from ATI are the newest, and both install more stuff and allow you to set more things.
If you install drivers from the CD or the ATI website, you must un-install anything you find Windows or previous driver installs have installed for the video in Add/Remove Programs, and/or you should un-install the listed Display Adapters in Device Manager before you install drivers.
I know from previous experience drivers and applications for ATI chipset cards must be installed in a certain order, and they are not always listed in the order you must install them on the ATI site. If you install those using the Setup or install on the CD that came with the card, everything will install properly, but if you get drivers from the ATI site they must be installed in the right order - there is a link to Uninstall, Install directions where you get the ATI drivers.
Installing updated display drivers found by Microsoft Update may result in the card not working properly. If you want to install updated drivers, go to the ATI web site instead to get them, and follow the directions - installing just the updated display drivers themselves may not work properly - you may need to, and I always, un-install all the old stuff, then install the new stuff.
You need a .Net Framework version as well for the Catalyst Control Center if you get drivers and apps from the ATI site - see the readme or release notes for the Catalyst Control Center version if that isn't obvious.
The CD may install a Control Panel, or Catalyst Control Center - if the latter it will install the .Net Framework version needed if it hasn't already been installed on your computer.
(.Net Framework versions are standalone - loading a higher version doesn't eliminate the need to install a lower version.)
"I'm trying to disable my VGA port, but I can't find that option under advanced controls"
"I looked for an option to set the DVI output as the primary port, but couldn't find that either."
" noticed that my secondary display, which is my VGA port, is set as default.
"So, to sum it up, I have my DVI port set to primary, but my secondary port says that it's default. Does this make any sense?"
I've never seen a video setting that can disable a card's port.
Windows normally sees the card's primary port as the default a single display is supposed to be connected to.
Cards with two or more monitor ports always have a display adapter listed in Device Manager for EACH port. You could try RIGHT clicking on the primary adapter there, and Disable it, but you may get no display at all in Windows itself after you reboot with the DVI monitor connected to the secondary monitor port.
If that happens to you, press F8 repeatedly while booting, select Enable VGA mode, go into Device Manager, and Enable the primary display adapter.
Rarely, another thing that can happen right after you install drivers for a card is you may then get no display in Windows, or at all, because the video drivers are not detecting your monitor properly. In that case press F8 repeatedly while booting, select Enable VGA mode, go into Display - Settings - Advanced - Monitor and set your monitor drivers to Plug and Play Monitor, or if you have the CD for the monitor, use Have Disk and point to the specific drivers for the monitor on the CD (it's looking fo *.inf files), save settings, reboot normally.
You should always install the specific drivers for an LCD monitor - the Plug and Play Monitor selection was not designed to support LCD displays other than LCD displays on older laptops, it has not changed since XP was first released, and though default settings won't hurt the monitor, you can choose settings when you are using Plug and Play Monitor that will damage the LCD monitor.
As far as I've seen goes, you can't change which port the card itself sees as primary - it's "hard wired".
As I said previously, if you have only one monitor connected, it is always the primary display in Windows, but that doesn't necessarily mean it's connected to the card's primary port.
I no longer have that Sapphire 9800XT card. I do have an ATI 9800 AIW on my other computer but it has only one (DVI) port.