OK, quick question. Can you move all data, including the OS (WinXP), from the master hard drive to the slave drive? If so, How do you go about doing this? If this belongs in a different Forum, I apologize.
You can't just copy the hard drive in use by the OS due to files in use and file permission/restrictions.
You can clone a disk. Which makes an exact copy, bit for bit. So say you have a 20GB HD and buy a 320GB and want to keep everything the same and not install a fresh OS, you can clone the small drive to the bigger and keep everything the same and have the extra space.
Going smaller?! Just make sure the 250GB has more than 50GB of free space so it can fit on the smaller drive.
I've always used Acronis. It works beautifully.
If you are looking for a free option, try http://www.ultimatebootcd.com/