Help Please: 500 gb Caviar won't assign drive letter automatically

Hey I have one of the GReen Caviar drives installed on my computer to back up files. I run Windows 7 and every time I start my computer and boot up Windows never assigns this drive a letter automatically. I can manually do it and store files on it, but it’s a bit of a hassle to do this every time I want to access the drive. The files reside on the drive and remain there even if you never mount it. Any ideas as to why it would do this and how I could fix it? Thanks for the help.

Youmay check if the drive isi free of defects by running en Extended Test using DLG.  You may also try using the drive in a different computer, in order to compare results.