If I understand correctly, you have a computer system working fine with an IDE hard drive, and you are trying to add a second HDD - a new SATA unit. You ask about using it as a "Partition" with the older IDE drive, but that's not the term used. I will assume you mean that you just want this new drive to be a separate drive with its own drive letter. SO, for example, you might have your C: drive you have always had and boot from, a D: drive that is your optical drive, and now a new E: drive that is the new unit.
However, you cannot get the computer to use the new drive that way. It does show up in BIOS Setup, but not in My Computer. That is normal. Any new empty drive must have two operations done on it to "Initialize" or "Prepare" it so Windows can use it. These are to Create a Partition, and then to Format that Partition. A Partition is just a single chunk of the physical space on the HDD unit that will be named and treated as one "drive" that Windows uses. You can Create a Partition of any size you like, up to the maximum space of the HDD unit. If you make one smaller than that, the extra space is just "Unallocated Space", and you can actually create a second (or more) Partition in that. The first time you Create a Partition on a HDD unit, a Partition Table is written to the beginning of the HDD that details exactly where the Partition is and how big it is, and keeps some space for more Partition information to be added later.
After a Partition is Created, you must Format it. This installs certain data file structures at the beginning of the Partition, according to the File System you have chosen, and THEN it is ready for your OS (Windows) to use for files.
The easiest way to do these things is with free utility tools from the website of the manufacturer of your new drive. Some drives in "Retail Packaging" come with CD's that contain these tools. Look for something that offers to Initialize or Prepare your Drive for Use.
Windows has a tool built into it that also can do these jobs, called Disk Management. To get there, click on Start, then RIGHT-click on My Computer and choose Manage. In the new window on the left expand Storage if necessary and choose Disk Management. Look in the LOWER RIGHT pane. It SCROLLS to let you see all the hardware devices it has. You should find your new HDD unit there represented by a horizontal block with a small label block at its left end. The label will have a name like "DISK_1", a size, and a couple other things. To the right is probably one large block called Unallocated Space. RIGHT-click on that and choose to Create a New Primary Partition. In the windows that pop up you can set the size to whatever you want (up to max), and do not make it bootable - you are using it for data, and plan to continue booting from your old drive, right? IF you also see here options for Formatting, choose these: use the NTFS File System and a Quick Format to get the job done in 15 miuntes or so. If you choose a Full Format it will do all the same stuff and then take MANY HOURS to run complete tests on the drive, not usually necessary on a new unit. BUT if the places where you set the Partition options say nothing about Formatting, just run the Partition Creation task first. When it is done, RIGHT-click again on that new Partition and choose to Format it. Then set the options as above and run this second task.
When you have finished this, back out of Disk Management and reboot your machine. You should find that new drive in My Computer ready to use.