hard drivers

1. Make sure that the jumpers on both drives are set correctly.
Your original C: drive should be jumpered as Master with slave present.
The new drive should be jumpered as slave.

2. Make sure that both drives are properly detected in BIOS settings.

I have seen a few instances where drives from different manufactures do not work well together. But, this is not as common as it used to be.

3. Once you are booting, a new drive needs to be partitioned and formatted.

In XP, you can do this from:
Administrative Tools,
Computer Management,
Disk manager

Right click on the drive, and select partition.
Create partitions as desired.
Then, right click on each new drive and format it.

Chas

In order for your computer to recognize the new drive, you need to identify it. If it's an EIDE drive, you need to designate it as the secondary drive (assuming you want your original hard drive to continue functioning as the primary drive). To do so, you must configure your new drive's jumpers, the little plastic and metal blocks that attach to pins in the back of the drive. The primary and secondary jumper configurations are determined by the hard drive manufacturer, so you will need to consult your new drive's manual to figure out how to place them

You could also put the new drive on the secondary IDE controller. You would still have to make sure it is properly jumpered as Slave or Master.