ATA means ’Advanced Technology Attachement' and is the serial interface for internal hard drives used by Apple since they abandoned SCSI many years ago. I would suggest you navigate to Other World computing Laptop internal Hard Drive replacement list: http://eshop.macsales.com/shop/hard-drives/2.5-Notebook/ You will notice they are listed as IDE (Integrated Drive Electronics). Don’t worry, this is the same as ATA. Pick out the one that seems right to you. They are a very reliable source for all things Macintosh. As you can see it is a very exhaustive list of drives made by all the major manufacturers. They also list the size of the drives and you should make sure the drive you get fits into the space that your old drive occupied. Good Luck jg On 17-Jan-06, at 10:56 PM, Jerry Krinock wrote: > We need a new hard drive for my wife's old 800 MHz Titanium > powerbook. The > hard drive is described in System Profiler as: > > ATA-4 Bus > IBM IC25N040ATCS04-0 > > It's 40 GB, but I don't know what "ATA" stands for, etc. Can > someone please > translate the above into some keywords that I could use for > searching eBay > etc.?