"One of parent hard disks of Windows XP Mode is missing"

I've used this site for good advice, esp by Kari to whom I send hopes for speedy recovery.

I'm trying to enable multiple users to access programs via XP mode, through Win7 64-bit computer (Win7 Professional).

Using Admin Profile, when trying to open Win XP mode within All Programs from Start Menu, I get this boxed message:
Win XP Mode - Windows Virtual PC
"One of the parent hard disks of 'Windows XP Mode' is missing."

I followed online help to again download XP Mode plus from MS website. Same error message.

Please read farther, if it would help to know what I've done.
Background: New Dell PC came with Win7 Home Premium. (detailed specs, if needed, are on my profile).
Used Admin profile to upgrade to Win7Prof, to use a large supply of business-related programs I used in XP.
Admin profile, used MS website to load and install Win XP mode, virtual PC, then update win XP mode (as instructed).
[Note: Now I think maybe I installed incorrectly, because I find Win Virtual PC under folder "Programs (x86)". But cannot find way to uninstall thru add/remove in Control Panel because XP Mode and Virtual PC don't show up as installed.]

Then I enabled a couple user profiles to access winXP mode via adding standard users as mbrs of Remote Desktop Users (under manage My Computer) - using guidance found on forum posts.
Sorry for being so lengthy compared with other posts. I just need to know how to start over, if that's what I must do. I did uninstall most programs I'd added after installing XP mode.

Thanks for any help you can give - I'm desperate, as solo business woman, to get PC working.
- Charilyn

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