I have a computer microphone question?

Whenever I record myself on the computer with my microphone the sound comes out really scratchy and isn't that clear and the microphone always makes a loud screetching sound. Is this because I have a cheap microphone? The brand is a Labtec, and I think I paid like $15 for it. My speakers are about $25, and they're cyber acoustics. I like to record myself singing or rapping, but it always is scratchy. Is there a good recording studio I can download for free to prevent the scratchiness? Do I need to invest in a good set of speakers or microphone? Please help.