Hello,
I recently formated my PC and upgraded to 64-bit Windows XP Professional from 32-bit Windows XP Media Center. Now that I have the OS up and running on my PC, I am having many problems. Sound not working and I can't connect to my modem (wirelessly and through ethernet/usb). This is not all. I'm guessing that this is being cause by not having certain drivers installed.
Story of my PC (don't read if you don't want to):
When I bought my customized HP Pavillion m7690e Media Center PC, I wanted to upgrade many things. I upgraded my video card from nVidia GeForce (forgot which kind) to nVidia GeForce 7600 GS. Then I upgraded from that to nVidia GeForce 8600 GTS. I also upgraded my processor to AMD 6400+ running at 3.2 GHz. I had all this with my 32-bit Windows Media Center OS. It also already had all drivers installed. Then I upgraded my RAM from 2GB to 8GB. When I installed it, my 32-bit OS only read 3.5GB. Then I read online that only 64-bit OS's support more than 4GB of RAM. That was my motivation to upgrade. So, I bought Windows XP Professional 64-bit and installed it on my computer, checked the RAM, and it read 8GB. But now, I'm having problems.
I go to: Right Click on My Computer -> Properties -> Device Manager.
I expand the "Other Devices" list and I see 6 yellow "?" marks for each of these devices:
Audio Device on High Definition audio bus
eHome infrared device
Ethernet Controller
Multimedia Video Controller
Unknown Device
USB Cable Modem
I've been looking online for 3 days now trying to find these devices. I can't connect to the internet on my computer now.

For the "USB Cable Modem", I'm guessing I need to use the CD that came with my modem to install the driver. I do that but I always get an error. I think that the no sounds problem on my computer is because of the "Audio Device on High Definition audio bus." What kind of audio driver do I need? What I'm most interested in is what is the "Ethernet Controller"? Do I need it for internet? And I don't know what the "Unknown Device" is. I really want to get internet on my PC working first. Then I can deal with the other devices.
Motherboard: ASUSTeK A8M2N-LA (NodusM)
CPU: AMD Athlon 64 X2 @ 3.2 GHz
Video Card: nVidia GeForce 8600 GTS
RAM: 4 x 2GB OCZ Gold XTC OCZ2G80002G
Anything else you might need?
I've checked HP, nVidia, ASUSTeK, and AMD for drivers but couldn't find any 64-bit drivers. I got my Chipset and Video Card drivers from nVidia but that's it.
Note: I also have this hardware installed on my PC:
Lite-On WN5301A 802.11 b/g Wireless Network Adapter. I think that this is my Ethernet Controller. I also tried searching for drivers for this thing and I founds some. But, they did not work. Or maybe I did not install them properly(I got a .inf, .cat, and .sys file) How do I install them? Where do I put them?
Please help me solve these device problems. Thanks. If you need any more info on my PC, just tell me here and I'll post it. Thanks again

I have SP2, btw.