EDIT: Use a USB installer with Snow Leo Install DVD restored on it and with NetbookBootMaker applied to be bootable for this to work. Explanation found here.
First off, Snow Leopard by default will only install on disks which use GUID as their partition scheme; Windows XP doesn't like that, cause being an older OS it wants to play only with MBR.
One solution is to just install Windows 7 instead of Windows XP. But people want to dual boot with Win XP for reasons they only know and that we should respect. It's their choice anyhow.
Ok, so it's gotta be Win XP, another solution is to hack the Snow Leopard installer to make it accept an MBR formatted hard disk as installation destination. It's doable, yes, but still requires work. I myself did not attempt this cause although there are good resources out yonder in the world wide web, there wasn't a thrust compelling enough for me to go down this particular path. Snow Leopard's happily running on the Mini. I didn't care enough to sweat it. Period.
So what do we do now? Look enviously at real Mac heads who can effortlessly configure Windows on their Macs to dual-boot with Apple's big cats? Not anymore.
Who says it's only them who can have the pleasure of using Boot Camp Assistant? Yep, a hackintosher by the name of "modbin" has graciously shared his talent with the community and brought us Boot Camp Assistant that will work on hackintoshes.
In a nutshell, Boot Camp Assistant is just a friendlier front end for the same old Disk Utility we've come to love (and hate at times). We obtain a partition on a GUID hard disk that Windows XP will want to install on.
So, here we go:
