mixer to sound card problem, need help ASAP

I am running this mixer's tape outs (output to recording device) via rca to miniplug to my computers mic port. The set up works, but, sound is terrible in a number of ways. It has to work TONIGHT, and i don't have time to go buy an actual recorder. I need to know if i can fix the problem with the equalizer (i hope) or do you think my sound card is the problem (not being able to handle the input). I think i can fix the problem with my mixer, because i've noticed that with lower volumes the quality increases, but this leads me to believe the problem is my sound card not handling all the input. So, would my sound blaster live from home handle it? or should i just stick with tweaking the equalizer??
thanks.