Yes, the enclosure allows you to install a regular 3.5" internal HDD inso as to make an external backup drive.
Personally, I wouldn't waste my money, as they are not all that reliable. There are a lot of conflicts between the manufaturer of the case controls and the manufacturer of the HDD connections and jumper settings. Then there is an issue about power problems as most external HDD pull more power than what is supplied within USB protocol so it may work or may not work.
The best external HDD are those that are manufactuered as a whole unit with their own power source and not USB powered.
If you wish to explore this avenue further because you have some old drives laying around and a few dollars to spare then go for it for the experience. You just may stumble onto a system that works for you.
As to the format issue...most of the external drives come factory formatted as Fat 32 so as to be used by more than 1 operating system.
To format:
plug in the usb connector and any outside power sources for the ExHdd...boot your system and allow windows to find the new hardware. If windows doesn't find it look in "device manager" under disc management and locate the drive. Right Click the drive and a drop down menue will show a format choice click that and follow the prompts as to what format you wish to use Fat 32 or NTSF(windows xp only)
Good luck!!