I recently got a DVD-Rom and hooked it up to my home stereo, but when I hook the sound card up to it, there is a loud humming coming from the speaker. Any ideas?

Soundcard to stereo or DVD to soundcard? Check what you're plugging it into - soundcards often have line and mic level inputs, which expect the incoming signal to be at different strengths. One causes low sound with a bad signal/noise ratio, the other can cause overloading and clipping. Humming is often caused by mains interference affecting the cables, so check that you're using well shielded wire and that it's not running over any power cables.

You have open ground/s (the braided shield) on your cable/s

I am familiar with ground humm effects over audio cables due to previous experience in TV engineering. The problem you are probably experiencing is caused by a difference in line potential between the computer's AC receptacle and the AC receptacle on your stereo system. It can usually be solved by leaving the shielding on your audio cable, that goes between your computer and stereo system, disconnected on one of the ends. However, you must use shielded cable in order to remove any additional humm contributed by other AC wiring. If you are unable to cut the shielding in the audio cable that goes from the computer to the stereo system, you can try placing a 3-prong to 2-prong AC adapter on your stereo system. If this does not stop the humm, you may need a special transformer between your computer's AC connector and the wall AC receptacle. You can usually get these at audio specialty stores. The other cause could be due to no ground connections in the AC receptacle at either end. To solve this, you will need to have an Electrician install a ground cable between the AC breaker box and the AC receptacle that your computer plugs in to. Audio humm problems can sometimes be a real bear to solve. Good Luck!

Also, check if you can reduce the output amplification on the card. Check for jumpers that allow you to change from speaker out to line out. Good Luck.

I had the same problem on my technics receiver. I was inputting into the phono hookup and would get that loud humming noise. A friend told me to hook it into the vcr1 or vcr2 inputs and that cleared it up. They use different levels.