Need recomendations for a new harddrive.

Potentially retarded questions to follow.

For use with XP, needs to be internal. And I'm gonna be buying it via Dell, so I'm refering to this shit. http://search.dell.com/results.aspx?s=gen&c=us&l=en&k=hard+drives&cat=prod&p=1

How much stats on my comp would you need for a good call on this? Also, I'm willin' to put in a fair amount of cash for this ($300+?), and I want a good one. What sort of specs should I be looking for?

>>10

The most direct way is to open your computer and look at the back of your hard drive.  The pin layout will look like what >>12 explains.  Also try googling to get a better idea of how to tell the difference.  There are plenty of "do it yourself" type sites that will explain how spot the difference and even how to install the new HDD.

You can also find the interface through the device manager.  Right click my computer >> properties >> hardware >> device manager.

Look for something called IDE ATA/ATAPI controllers or similar.  In here it'll list the SATA and ATA controllers on your motherboard.  If there are only ATA controllers or SATA controllers then you are done. 

If not, right click a controller, goto properties and look at the "primary channel" and "secondary channel" tabs.  On each tab it will show you the master or slave drives on that channel, if any.  The devices you will find here will be things your Hard disk drives, CD drives, and DVD drives.  Now you can either search until you find the HDD you want to replace (and thus figure out what interface it is) or you can search until you find a free spot, and buy a drive with whatever that interface is.  SATA is the newer and superior technology so definitely choose that if you can.