Interesting question which I normally wouldn't respond to because I don't know the "right" answer. But as nobody else has offered any and I have a couple of ideas that should work, here goes:
First, if you are a member of .Mac you can use Backup to burn all your data to DVDs and "sneaker net" them to your PC. Could be a LOT of DVDs, tho.
Second, create a new user account on your Mac, then delete your current account. When you do you'll be asked if you want to save the data in the account: obviously you do. Your Mac will trundle for quite a while and then you will find a file under your old user name in the User > Deleted User folder. Just copy this file to your PC via the wifi network and Bob's your uncle. Beware, however, that this method will NOT preserve applications, just the contents of your User folder. But your Mac apps won't run on the PC anyway so...
Third if you have enough hard disk space you should be able (theoretically) to create a Disk Image file of all the contents of your drive, and then wifi that over.
Finally the fastest easiest but most costly way would be to buy an external USB2 hard drive, make sure it's formatted as DOS FAT, copy all your files to it, move the drive to the PC and copy everything over.
I am POSITIVE there are better ways but these should work if not be the most convienent. Good luck.
