A few questions to the OP:
What exactly do you want, and - more importantly - what exactly do you already have?
For gaming:
Ok, you've got Windows 7.
What games do you intend to play?
Do you use speakers or headphones? Do you already have an amplifier/receiver? How will you connect to your computer - analog or digital?
For audio:
You want to record guitar.
Acoustic or electric?
What about amps or mics, do you already have those and if so, what kind?
Do you intend to record more/different stuff (other instruments, vocals etc.) in the future?
And finally: What's your budget?