Well... you're gonna need a Windows disk.
Either scrounge up a WinXP Volume-License disk (nice!) or else buy a Win7 Home Premium disk for whatever, $100 bucks.
If it's an older laptop with 4GB or less memory, just stick with the 32-bit Win7.
Though I like WinXP fine, and have it running on a big quad-core home rig, I don't think you can buy it anymore...
Plus I guess it's going the way of the dinosaur, anyway. They say Microsoft Update won't be supporting XP too much longer.