All current IDE drives are at least ATA-100, most are ATA-133. It's all backwards compatible. You can run a faster drive on a slower interface (eg. if your motherboard only supports ATA-66) adn you can run a slower hard disk on a faster motherboard.
You can connect multiple drives to your computer and copy the files over. You should re-install Windows, though, or you will have to use software like partition magic to copy the entire window partition.
TheMajorMMX - Intel P200 MMX @ 225Mhz - V-Tech (PcPartner) Baby-AT mb w/ Intel Triton TX chipset - Nvidia Riva TNT2 M64 w/ 16MB - 256MB M-Tec SDRAM - Still running.....