My girlfriend needs to upgrade her computer,so i said ill give it a try!! Gateway Select 950 Athlon 950MHz 384 MB Ram- 20-GB 4500 RPM Ultra 100 Hard Drive-ATA/66 40pin 80 conductor cable Now,I can install the memory no problem,512MB memory stick. I need help with the hard drive.Shes a school teacher and 20 GB is really way too small.Its almost full.Im thinking about 80GB should be good for now. My question is,Do i have to use a ATA/66 or can a ATA/100 be combatible.Then how shoul i clone the drive?Or should i just install it as a backup drive,as the slave.ATA/66 is fine,its just the one i got picked out is 80GB ATA/100 7200RPM.Is that combatible? If anyone knows?