Here's my system (for background reference):
- GA-8KNXP (Rev 2.0) motherboard
- Intel Pentium 4 2.6GHz CPU with 800MHz FSB
- Kingston KHX3200K2/1G HyperX DDR 400MHz 2-2-2-6-1 Dual Channel memory pair (1GB total)
- Antec 1080AMG case with 430W TruePower supply
- Two Maxtor 6Y120M0 120GB 8MB buffer SATA hard drives (in a RAID 1 set)
- ATI Radeon 9600 128MB AGP 8x video board
- Memorex 52MAXX CD-RW
- Memorex 16x DVD
- Diamond PCI 56K Modem
My ATI Radeon 9600 came up no problem. I ran all the Direct X tests and everything passed. (One interesting thing is that even though I bought a straight "9600" board, all of the system device information displays it as a "9600 Pro" board. I don't know why this is. The box clearly says "9600" without the "Pro" indication. But I'm not complaining!
Is everything else within your system working properly? If so, then it's either a BIOS setting or driver issue. Go into the BIOS after booting up and check all the settings for the AGP. (I think it's under one of the advanced menus, but I don't think you have to hit <CTRL><F1> to get to it.) It should show you if the 8x AGP is recognized. Other menus will also show the AGP bus settings. If the settings all look okay, go to ATI and get the latest Catalyst drivers and re-install them to make sure you are up to date.
You might also want to download the latest version of Direct X. I think it's up to 9.0b.
If none of that works, then there is always removing and re-installing the ATI board to make sure that pins didn't get mis-aligned or crunched (in the socket) during the initial installation.
Regarding the on-board sound issue, first, make sure that you loaded the sound driver from the Gigabyte IUCD utility CD-ROM. Then follow the direction within the installation guide (I know, it's a novel idea that I neglected to do as well) and click on the "sound effects" icon on the taskbar. Go through each menu and make sure that everything is set up properly for the configuration of sound system that you are using. In my case the auto-port-detect mechanism was turned ON by default and incorrectly set my speaker output to be a line input. Needless to say my sound didn't work. I just got popping or snapping sounds everytime Windows started up or generated any sound. Once I disabled the auto-detect and set the ports to my configuration my sound worked fine.
Hope this helps. My system's now been stable for a couple weeks without any crashes. My only current problems are finding that Microsh$t has rendered many of my old software utilities useless under XP. I'm currently considering creating a FAT32 partition and "upgrading" to Windows98 so that I can run some of them again...