I see you have made the same thread on some other forums also, Eh! RobertQ.
Well, there are vista drivers for the ATI X600 here.http://www.nodevice....0/get44362.html
Broadcom drivers are here.http://www.broadcom....eme_desktop.php
I would discard the conexant modem and if you need one buy a vista capable PCI modem. I really don't know why you would want one when most people go for the cable or telephone ethernet hi-speed internet. You already have the Broadcom ethernet in the computer.
SoundMAX Integrated Digital Audio
Microsoft Windows Vista build 5308 uses Windows Update (herein called WU) to get the latest drivers for the SoundMAX chipset. These drivers stutter, hiss, snap, crackle, and pop, nonstop and do not have support for digital audio. This is an improvement over 5270 where you had to find your own drivers, AND it was impossible to get digital audio.
Drivers are here.http://neosmart.net/...-sound-drivers/
It would probably be better to buy a Audigy 2 sound card and install it if you want good sound.
The hardware above is why Dell says not to upgrade. If you do go ahead and install Vista i would suggest the replacements above.
On most of the drivers i would find and download drivers to the computer before installing the new hardware. Then install the hardware and boot the computer. When the "found new hardware" windows comes up, cancel the install, Click Ok on the "Hardware may not work properly" window, then Double click on the downloaded drivers to install them.
Check on the ATI website on doing this because they may want you to install the drivers first( not likely). I know you can do the install before drivers on the Audigy card if you decide to buy it. The other drivers you can also click cancel and install downloaded drivers for the Ethernet and soundmax sound.
Good luck with this endeavor.