Converting an external hard drive to internal

I have a WD Elements 1 TB external drive. I'm in a pinch and I need an internal SATA drive.

How do I find out if the drive in here is actually a SATA drive?

Edit:
The WD Elements is a really nice external drive. I gently pried open the top and slid out a 1 TB Caviar Green hard drive. There were four black rubber brackets that slid off easily. One screw removed the SATA --> USB, and then I slid it into my computer.

Since it's 1 TB in size, it's almost certainly a SATA drive. You can crack the case open and find out for sure, but make sure you're okay with voiding the warranty (if it's still under warranty). Unfortunately, many external hard drives have concealed and/or tamper-resistant (i.e., nonstandard) screws, so it may not be possible to open the enclosure without breaking the plastic or drilling out the screws. Then again, it is possible to purchase screwdrivers that can remove certain types of tamper resistant screws (such as Torx drivers with a hole in the middle of the Torx head). If you don't want to use the enclosure again, or if you don't care how it looks afterward, this might be an option.

If you don't want to void the warranty and/or you need to reuse the enclosure and want it to look as unmangled as it does now (but can't find the right screwdriver to remove the tamper-resistant screws), you might want to buy a new internal drive instead.