I thought you could go to an apple store and buy it for a PC
There's, as Motoxrdude said, FL Studio, and then there's also M-Audio Session (which I've never used... it's supposed to be similar to garageband from what I've heard.)
m-audio session is a great little program. I tried it for a while when it came with a midi controller i bought till i got cubase. If its a pay program, i can send you the disc since im not going to use it.