How do I sample sound direct to my PC?

The mic I want/plan to use is a boom mic and, I have a computer.
(Question in thread title.)

Ben Dover wrote:The mic I want/plan to use is a boom mic and, I have a computer.
(Question in thread title.)

What actual mic are you working with?

There is no such thing as a "boom mic". There are however boom polls to mount microphones onto....and there are also microphones.
Clearly stating what equipment you have is the first step to getting the best help.

There are a few ways you could go:
1) Computer based:
If you want to work with a laptop or desktop, you'll need to get an audio interface.
I suggest something by M-Audio as they have stable drivers and great products for the price. I like the Fast Track Pro.

2) Portable Recorder/MTR based:
These small hand-held recorders have really advanced within the past few years.
My number one choice is still the Zoom H4 as it has good on board mics but more importantly, it allows you to plug in XLR connected mics.
Tascam also makes some fine units in this field as well.