How do I correct an incorrect but embedded Apple ID in order to be able to access the App Store?

Question

I recently installed Yosemite 10.10.1 in my iMac,  Upon receiving notice of upgrades available I attempted to access via the App Store as required.  I was directed to enter my :Apple ID and password;  however, an ID was already entered and it was not mine.  Any attempt I made to highlight and correct the ID failed - it was unresponsive.  I attempted to use management of my account to verify the correct ID;  the file showed my correct ID but when I attempted again to log in to the App Store the same incorrect and immutable ID appeared. The incorrect ID is that of my wife for her OS 10.6.8 laptop.

Answer 1

1. Triple-click anywhere in the line of text below on this page to select it:
kMDItemAppStoreHasReceipt=1
Copy the selected text to the Clipboard by pressing the key combination command-C.
2. In the Finder, press command-F to open a search window, or select
          File ▹ Find
from the menu bar. In the search window, select
          Search: This Mac
from the row of tokens below the toolbar. Below that is a popup menu of search criteria, initially showing Kind. From that menu, select
          Other...
A sheet will drop down. In that sheet, select
          Raw Query
as the criterion, then click OK or press return.
Now there will be a text box to the right of the menu of search criteria. That's where you enter the raw search query. Click in that box and paste the text you copied earlier by pressing command-V.
3. The search window will now show all the App Store products that are installed. Compare those search results with the list of your purchases from the App Store. To see the complete list, you may need to unhide hidden purchases. If any apps were download from the App Store using other Apple ID accounts that you control, sign in to the store under each of those ID's and check the purchases.
4. At least one of the apps in the Spotlight search results is not among your purchases in the App Store. Move each such item to the Trash, after quitting it if it's running. You may be prompted for your administrator password. Empty the Trash.
5. Quit and relaunch the App Store. Test.
If you find these instructions confusing, ask for an alternative method.