I have an older laptop computer with a IBM Travelstar 4GT 3.2GB 2.5inch 4000RPM HD. Iwould like to know if I can replace that with newer model HD from IBM such as a Travelstar 5K80 20GB or 40GB 5400RPM ATA-6? Also, I would like to know the difference between ATA-3 and ATA-6? My old HD is a ATA-3. OS is Windows 98, 128mb ram. Thanks