Before asking a technical question do the following:
Try to find an answer by searching the forum.
Try to find an answer by searching the Web.
Try to find an answer by reading the manual.
Try to find an answer by reading a FAQ.
Be precise and informative about your problem
Describe the symptoms of your problem or bug carefully and clearly.
Describe the environment in which it occurs (machine, OS, application, whatever). Provide your vendor's distribution and release level (e.g.: Windows XP SP1, Ubuntu 12.04 32bit, etc.).
Describe the research you did to try and understand the problem before you asked the question.
Describe the diagnostic steps you took to try and pin down the problem yourself before you asked the question.
Describe any possibly relevant recent changes in your computer or software configuration.
If at all possible, provide a way to reproduce the problem in a controlled environment.
if it a new install check the bios first to see if it seen. if it is you have to use windows disk tool to make it active and give it a drive letter or use third party tools. http://www.youtube.com/watch?v=Svb7j3GnB7c
when you open disk managment you see a drive that will not be active or have a drive letter. windows will have to make it active and give it a drive letter.
if the drive is not showing up in the bios check that the cables (both power and data are on right).
on mb check what port your using. some mb have two sata chipset the intel/amd ones and third party chipset. if you plugged the drive into the thrid party chipset you have to turn the chipset on in the bios. also check in the bios that the sata ports set to achi not ide or raid.