Ok, if you are looking to get busy using your computer then....
For free you can checkout:
Pro Tools (FREE) (works on all macs, but Win98 on PC only)
a toned down version of digidesigns mammoth audio recording/sequencing application.
Audacity
a free wave editor. Fine tune your samples and wot not with this.
Kristal Audio Engine
This baby will probably not be free for long...try it out. A sequencer, editor and mixer with bells on.
Then the not very expensive pro ones to checkout are:
FL Studio
This is my weapon of choice. Download a free demo at the site.
Reason
Very good sequencer, jam packed with instrument and effect racks.
Project5
Cakewalks soft studio is like the above two. Accesible and fun.
Acid Pro
Nice for it's auto pitch shifting of loops. A good alrounder.
You could always tear up your Dad's record player tho
Oh and purchasing the magazine, Computer Music monthly comes with a CD full of free software hosts, synths, samplers and loads of samples to get you going.