This is pretty easy with Windows XP. First
turnoff computer and unplug it. If you have your computer open ground yourself so no static electricity hurts your computer. This can be done by touching the chassis of anything electrical. Like a metal lamp thats plugged in.
If you only have one hard drive now, you should already have a IDE connector free. Just trace the big looking plug from your existing hard drive to the empty one plug, thats the one to use.
Now you need to make the storage drive a slave to the master (your existing hard drive). This is a easy jumper setting on the back of your hard drive. Sometimes the drives are marked sometimes not. You are looking for Slave or SL.
Still can't find it. It is the set of pins right next to the power plug. Most slave jumper settings are two in looking from right to left. Look at your master setting, it should be three in from right to left.
In most cases the hard drives are grouped together, install your storage hard drive and plug it in just like the master. Re-plug your computer and turn on.
Windows will see the drive but you must go into "My Computer" and right click the new drive. Go down the list and click fast format or format.
After it's done Restart computer and viola!
Hope that helps.
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Your Hardware Guide.