Vista - Can't access external HD

Hi guys,

I plug in my HD (Western Digital Mybook 640GB), and it recognizes the device, but I can't seem to access it to do anything with the files. It doesn't show up in My Computer. I've gone to Disk Management, and it shows up as "Disk 1" but when I right click the only executable options are "Convery to Dynamic Disk", "Properties" and "Help" I plugged my USB stick into the same slot and it works fine. I searched a similar thread and it was recommended to make a new partition, and assign a letter to the drive, but I don't seem to be able to do this?

I know next to nothing about PCs (I'm a mac user ), I built this myself last week to run a few specific programs, and everything has been working fine except for this. I'd appreciate some very clear help taking into the account the fact that I know nothing, lol.

Thanks!

go here:
WD Support > Downloads > My Book
find your WD and download the "All" software and reinstall

most external drives come with security software that locks the drive. that way, if its stolen, somebody cant just plug it in and steal your data.
to get mine to work on a different computer, i had to run the disk management software that came with the external drive, and disable the password protection feature.