If you're really into this, or just want a better computing experience,
get a Mac. Apple includes
GarageBand on every new Mac as a part of iLife. I use GarageBand a lot and find it really cool whether you make your own songs from scratch or record live instruments to tweak later.
A step up from GarageBand is
Logic Express. Logic Express is a toned-down version of Logic Pro, but it has most of the fundamental features to really dive into musical editing and recording.
Logic Pro is an all-out editing/recording machine. There are tons of features and effects that makes it one of the most comprehensive programs on the market.
Soundtrack Pro is also a program for scoring your movies, and blends perfectly with
Final Cut Studio.
You can also use Audacity and other free-ware & shareware apps on the Mac.
If you get a new Intel Mac, you can also boot Windows and/or Linux with OS X.
I made the switch a year ago and never looked back. Working with an iMac is Teh Win!
[I'm not associated with Apple
]