HDD that worked under Vista suddenly gone?

I have three large hard drives in an external USB enclosure - one 1.5TB formatted as NTFS, and two 1TB both formatted NTFS (I think). All three disks worked perfectly under Vista and, from time to time, on a Mac I also use at home. I recently upgraded my PC to Win7, and suddenly, two of the HDD are no longer available for use. I go to My Computer>Manage and select Disk Management, and the disks are there, but the each show a 200mb EFI partition, then the 931gb (Health) Primary Partition - but all of the options are grayed out on both drives.

I have a ton of data on these that I intend to keep; is there a fix for this problem, or do I need to uninstall Win7 and go back to Vista?

Thanks in advance for your help.

The upgrade path was definitely the wrong choice.

You may have deleted all you files on a particular partition.

An upgrade leaves hundreds of useless files on your harddrive and can cause driver conflicts.

Go to Start > Run, and type diskmgmt.msc, expand the windows so everything shows,then hit the Alt + PrtScrn and post that as an attachment here.

Here you go...

[IMG]file:///C:/Users/Owner/AppData/Local/Temp/moz-screenshot.jpg[/IMG]Hope that helps.

It appears you've installed Windows 7 to disk 2 and disk 3

There are no drive letter s assigned with these drives either.

It seems obvious that you did not perform a "clean" installation also an you have the 200 MB partition.
It's common for this Boy to have a drive letter assigned to it.

I'm no dual-boot expert, but look over these results:
200mb EFI partition - Google Search

I'm sure someone with a better understanding will come along to help you out.

Actually, Win7 is installed on Disk0 (C, although disks 1, 2, and 3 were all installed in the machine when the installation was performed (i.e., they were temporarily removed from the USB enclosure and installed in the tower). Kind of hard to fathom that the upgrade process would monkey with hard drives that weren't the installation partition, but I'm no Windows genius. And no, I don't think I did a "clean" installation. Again, not sure why that would affect extra hard drives, but who knows?