|"Product: Dell Dimension 3000 desktop - customizable"|
If that model is correct and it truly is a customized model, the possible installed hardware components (cards) varies.
Did you search using the Service tag number, found on the back of the case, on the Dell site to find the downloads for your exact configuration ?
Sometimes, you also need to search using just the model, in this case Dimension 3000, to find all the available downloads for a customized model. E.g. One of those may be what you need for the SB card, if it's a physical card.
Did the SoundBlaster card come with the computer, assuming it's a card in a slot?
Remove the power cord to the computer, remove the sound card, and find the model number on it - SBxxxx or CTxxxx - and tell us what that is.
NOTE that the SB card should NOT be installed in the last PCI slot of the PCI slots closest to the center of the mboard - only PCI video cards will work with that slot properly, because that slot is forced to share it's IRQ with the video.
Windows can't show you your DSL modem as a device directly, but you can find out if it is being detected, with ipconfig /all in cmd mode, but we need to know if you are also using a router.
Are you using a router between your computer's network card and the DSL modem?
(If you are, Windows CAN show the router as a device in your network configuration, if you change a default universal PNP - UPNP - setting).
If you are, some DSL ISPs require that router is set to the same MAC address as the network adapter on the computer (you clone that MAC address in the router's configuration, rather than using the router's own default MAC address). However, if that was correct previously and you haven't changed any router settings since, that is still correct and your DSL connection should work.
Windows assumes you don't need any custom settings to connect to the internet - sometimes you do have to use custom settings. The ATT web site would have info about that.
Assuming you don't need to use custom settings to connect to the internet, or in any case, when you have installed Windows from scratch, you often need to inform Windows of how you're connecting to the internet, initially.
Go to Control Panel - Internet Options
(or start up Internet Explorer - at the top of the screen choose Tools - Internet Options)
Click on the Connections tab.
Click on Setup at the top of the page.
If you do that correctly, you should then be able to connect to the internet. You may need to reboot, or to close Internet Explorer and go into it again.
Assuming you did find the correct drivers and associated software for the sound card, people often install the software incorrectly.
Unless the instructions for installing a device tell you otherwise.......
You DO NOT install drivers for a device while booting into Windows, if the software for the device has not been installed yet - when Windows finds a generic device or New Hardware while booting, you allow it to search for drivers, it doesn't find any, and it wants you to show it the location of the drivers - CANCEL that, continue on to the desktop, and install the software for the device using the proper installation from a CD or the proper installation file that you downloaded from the web.
In the case of a sound card or onboard sound, the software includes associated software that must also be installed correctly.
If you DID install drivers that way, go to Control Panel - Classic View - Add/Remove Programs and Un-install the software you installed, reboot, DO NOT install drivers while booting, and install the software the right way !
The same applies no matter when Windows finds New Hardware !