I agree with the fact that good gear won't make up for bad skills. Period. I pulled miracles with bad gear, and now that I could afford it, I have great gear.(I'm also not a DJ, my audio desk cost me way over $40K ALONE, not to mention the $26K in custom wiring).
As far as things not working. First, you really should NOT use your soundcard when doing pro audio, even DJ'ing. Your sound card interface will suck for the most part, even if you have a good one. One of the key issues is that you need to have a line out, which is not that hard to accomplish. There are cards with dedicated line outs, or you can move a jumper to disable the amplifier op-amp and turn the headphone into a line out. Or, you can use an active direct box(stereo preferered to make your life easier and fewer gadgets to lug), but that requires phantom power and you'll need XLR inputs to your source.
Internal sound cards get tons of noise due to the lack of proper shielding in there. For anywhre from $60 to "gee, how much do I want to spend...", you can get yourself an external audio interface, which resolves many, many problems.
Seeing a DJ use Serrato(older version but he still uses it, I just did yet another show with him), it was hard for me to wrap my head around it. I'm used to seeing a turntable and stylus being used as a sound source not as a controller, despite the fact that I get the concept of the discs are controller discs. Audio sourced on hard drive, 2 windows for source playback, window for cue. 2 sets of inputs and outputs on the Serrato interface(2 for turntables as control, 2 for OUTPUTs for source playback) and then those 2 audio outs go into his DJ mixer. It's a great concept and it jus works. But, something like this, I would suck at because I'm not a DJ and that's not what I do. But I like the whole concept and I really like how these systems work. Gives you that old school look and feel with modern digital performance(except scratching isn't as organic).
Of course, I recommend Firewire over USB for audio interfaces because it just flat out works better and isn't half duplex. But if you're only going one way, then hey, USB is fine as long as you're USB 2.0.
All DJ's need to do themselves a few favors from time to time. Get off the sound cards and go with an external interface. From there, it tends to be much smoother sailing. You'll appreciate the boost you get from better quality sound.
I also hear the issue of "I don't want to learn this, or that...". Yup, most of us will go through this phase. Some of us are lucky enough to not have to get past it, but in some cases, we have to. In my case, going from analog to digital live sound, its a learning curve, no doubt about it. I am also hesitant to move from MyDMX to Compu Live because frankly, I really like MyDMX. The fact in my situation is that I do need to move forward, like it or not. My excuse right now is I just can't deal with it until after my next big event, coupled with Elation is about to bring out new hardware and software, which helps force a waiting period as I wait at least 6 months for new software packages to ensure they are stable and less buggy.
DJ's have a wide choice of options, in features, quality and pricing. It does come down to what works best for you. Thank goodness there are choices, as wells as the choice to not use certain things.