When selecting a hard drive size is not allways the most important factor. Where a large drive is great and faster drive is better for your boot drive ie C:/ drive Windows cache's the hard drive quit heavy and a 4200rpm drive just cant cope with the pressure where a 7200rpm drive often will. This is often the difference between a better built computer system and a economy model. I often here the remark " My friends computer boots and performs better then my computer yet i have a slightly faster CPU". In closing look for a faster speed drive with more cache memory at the size your after and you will be more happy with your drive. Poor 4200rpm no cache Great for project's. better 7200rpm 8 meg cache Great Boot drive all round performance. best 10000rpm 8 meg cache Great for file server,s and hard core gamer,s. ide sata scsi? this is often not important as you will need to buy the drive supported by you computer. IDE works great, SATA is a little faster, SCSI is for web/file server,s.