Video card issues on HTPC

So I recently upgraded a Dell Vostro 200 PC to use as an HTPC. Here's my current config, the only upgrades from original are the video card and RAM.. and an external HDD.

• Processor, E4300, 1.8, 2M, Core Duo-Conroe, Lonsdale/Lavaca
• 160G HDD, S2, 7.2K, 8M, LEAD FREE..., SGT-NH
• DVD+/-RW..., 16X, Half Height, BARE, Hitachi Lg Data Storage
• 4 GB RAM (Upgrade from original)
• ASUS EAH5450 SILENT/DI/1GD3/V2(LP) Radeon HD 5450 1GB DDR3 PCI Express (Upgrade from original)
• Windows XP SP3

I'm having a mix of issues out of the video on this. It came with integrated video on the motherboard so I'm curious if that is causing conflicts. I have disabled the on-board video in Device Manager.

ISSUES

The resolution resets itself all the time. I can't set the resolution from within the system settings as it will only let me choose 640 x 480 resolution. I have to use the app that came with the card. However if I turn the resolution up it resets when I restart the computer and also when I exit XBMC.

Computer won't display at all after bootup, just black screen, but I do see both the Dell and Windows splash screens while booting. This has happened twice now and the first time I had to use system restore to go back a couple weeks to get it "fixed". The computer is booting to the desktop but no display. I know it's booting up as I have a WiFi keyboard app on my iPad and I'm able to shut down / restart it so it is launching the server app. I also have LogMeIn installed and I'm able to login to the machine but I still see a black screen on the remote display. BUT, last time I disconnected from LogMeIn the screen flash an image and I saw a box that said something to the effect of "No Video Hardware Found".

The thing that confuses me the most here is that I see the Dell and Windows splash screens so I need it's sending the video signal, it just goes totally black once it boots up all the way.

As always, any help is appreciated. I've asked a ton of questions on here and want to thank everyone for the help in getting me this far!