External Hard Drives Gone After a Restart

After a reboot my two external hard drives have vanished from my PC. I've had one of them going on five years and the other for only six months. I really can't believe they would just break after a simple restart. Especially two of them at once.

Folder Options are set to detect hidden files/drives so they aren't just hidden either. I tried uninstalling the drivers and letting them reinstall, but it didn't make a difference, when doing an error check and along the lines of "Windows can't detect this drive."

This is quite interesting. I thought it was an error with my WinXP updates on the laptop. After the weekly updates two weeks ago I got that same error with the suggestion to reformat the drive. Since it's got my computer life on it I unplugged. Although I do have cd and dvd backups I still would like to recover the data. I attempted on the Win7 64-bit desktop computer to get it up and with another desktop WinXP 32-bit and they all had the similar error (wording just a smidge different). I came in here to see if I could find a good recover software to be honest when I saw this post. I will be anxiously awaiting any responses as well. Perhaps there was an issue with the update(s) recently???

sorry it took awhile to get ahold of another pc :)

After plugging it into another PC it will show up under the Disk Drives section of Device Manager, but it still appears to be hidden when going to My Computer which is more-or-less what happens on my PC as well. Its like the drives install but are simply hidden. Both computers are running the same version of Win7. I also tried the system restore and that didn't seem to work.

When I went into Disk Management it asked me to initialize the disk for Master Boot Record or GUID Partition Table...never really asked me about these before since I've never had any problems so I'm not sure which I should do (?)

I also looked into Computer Management. In there it also shows Disk as Unallocated/Unknown/Not initialized (put a screenshot). In Device Manager it's the Hitachi.

If the drive were empty to begin with that would make the solution a bit easier I think, heh. Just right click it and "New Simple Volume" I think would do it. BUT if there was data on there I'll throw up my hands in confusion and my ineptitude at that point will carry me far away in a corner of the room and wonder why it all happened.

The drive has alot of data that I really don't want to lose. I know there is stuff like you mentioned before Recuva to get back deleted files, but I've never had any luck with these sort of programs.