Cant Use Sound Mix Properly!

[Mrkakarot]

hey all, been trying for a long time to get y sound mix working, im trying to record my first lets play and its being weird, its either i can get really good mic quality and not good sound.or good sound quality and a rubbish mic sound, iv got an acer aspire 5720. and its pretty good and can do lets plays as far as im aware, does anyone know why icant use good mic and sound? im looking at getting a new sound card for my computer to see if it works, but iv only got £30 ($58) to spend as im not sure my computer is even got a sound card, well any help would be greatly appreciated thanks all