Where'd my HDDs go?

Hello, all - brand new member here. Good-looking forum, looks like it has a lot of useful info. I did a search for this, but didn't find anything exactly like what I'm experiencing (found a couple of things that were close, tried those solutions, no dice).

I just installed W7RC into a partition on my main hard disk (by "main" I mean a 1TB drive with Vista Ultimate installed in a 900gb partition and W7RC in a 100gb partition on same drive). I also have 3 other SATA drives in the case - none of which show up in Windows Explorer. They all appear in Computer>Manage>Storage>Disk Management, but when I right-click on them, the option to assign a drive letter is grayed out.

When I boot into Vista, the drives are all available.

Any idea what's going on here? Thanks in advance for any advice you can offer.

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