How to update driver/s for WD250GB (My Book Essential Edition) external hard drive for Windows 7

I have purchased a new PC that has a 64bit Windows 7 operating system.  I have attached my WD 250GB external hard drive to the PC but  it will not operate.  The drive is used only for back-up purposes.   I assume I need to update the drivers but am concerned about doing so from websites that are neither WD or Windows websites.  Can someone please advise where is the safest place to locate the latest driver/s, assuming that is all that is required?

Is my external hard drive compatible with Windows 7?   Thank you.

You should have been asked to install the SES driver.  Check Disk Management.  Does the drive show up there?