You cant remove ur current HDD, because it has Windows XP on it, and everything u have on ur PC is on it.
I mean u could remove it, but then ud have to install Windows on the "new" one.
What u must do, is check what kind of connectors the HDD has, and wich ur motherboard has. Its probably IDE and so is ur current HDD. If u have only 1 HDD right now in ur PC then u could connect the "new" one as a slave to ur current one and that would work fine, or u could just connect it to any IDE connector if u have any extra, but thats really a waste of space.
Your best option would be to leave the current HDD inside and just ADD the "new" one.. i mean its bolted in there. Do u even know how to install an HDD?
Also, the HDD that u found, has less then 10GB, probably 5 or 2GB. So its really not worth it.