USB 2.0 is a hardware standard/device and can't be downloaded. Newer
computers have it already installed. To put USB 2.0 on an older computer you
would need to purchase a USB 2.0 PCI card for a desktop machine or USB 2.0
PCMCIA for a laptop (PC-CARD) and install it in your computer.
You also need SP 1 or 1a from Microsoft to enable USB 2.0 on your XP
operating system.