Switched computers with hard drive not recognized now

I had my external hard drive plugged into my Vista computer, until my vista took a dump.  Luckily I got all my pics etc on it before then.  I tried plugging into my laptop which is a xp, but it is not recognized.  Everything on external drive is turned on and lighting up.  But when I pull up my drives it does not find it at all.  Also, my drive is locked so I have to be able to unlock, which is kind of hard with out it finding the drive at all.  Any suggestions on what to try? 

I have tried the microsoft fixit, and that did not find the drive either. 

Hi there, what capacity is the drive and was is formatted on Vista? If by any chance you formatted the drive as GPT then XP won’t see it.

Also, did you check on disk management (Right-click my computer/computer) to verify if the unlocker is just not given a drive letter?