My Passport not recognize on Vista

I recently purchased a 500GB My Passport Essential and used it for about 3 or 4 days with no problem on my Vista OS laptop.  I transferred some video files to the Passport, then noticed they were still on the internal HD.  I selected them on the laptop and began to delete them.  A few minutes later discovered the videos were also deleting from the Passport.  I hit cancel, then disconnected the Passport to prevent them being deleted any further.  WHen I reconnected the My Passport portable HD, it was not recognized by the computer.  It shows up in the Device Manager, but not in the computer.  I have tried refreshing the display and rebooting the laptop.  I took the My Passport to work and connected it to my desktop computer running XP, and had the same problem until I hit F5 while in My Computer, then it showed up.  No such luck on the laptop running Vista.  Reading the posts didn’t seem to give me any solutions.  As far as I can tell, there is no “Disk Management” on Vista, only the Device Manager that shows I have  connected a WD My Passport 071A USA Device and a WDC WD1600BEVS-22RSTO.  Clicking on the “Safely Remove Hardware” icon in the task bar simply says, “Safely remove USB Mass Storage device.”  I specifically bought the Passport to free hard drive space on my laptop, which now cannot even see it!  How can I get the laptop to recognize the external hard drive, assign it a drive letter and make it usable???

There is disk management in Vista. I don’t have it handy now to look so this is from memory. Go into control panel then Administrative Tools, Computer Management, look in upper left corner it should be there. Were you using some type of backup or sync software? I don’t understand the deleting  problem. It’s never a good idea to trust important files to just one physical drive internal or external. The forum is full of posts where they did what you intend and have a problem.