QuickBooks Point of Sale & QuickBooks Enterprise

1. Open Windows Explorer (right-click on the Start button and select Explore)
2. Double-click on the C: drive
3. Show hidden files and folders (Tools > Folder Options > Select View tab >Hidden files and folders > select Show hidden files and folders > Click Apply and OK)
4. Show protected operating system files (Tools > Folder Options > Select View tab > Deselect Hide protected operating system files > Click Apply and OK)
5. Right-click Config.Msi folder and select Rename
6. Add .old to the end of the filename and press Enter (the folder name should now be Config.Msi.old)
7. Hide protected operating system files and hidden files and folders again (following Step 3 and 4 above, but hiding, instead of showing)
8. Now update, repair, uninstallation or installation should complete without error

If this doesn't work, it sometimes helps if you download the update manually from the Intuit website:  QuickBooks 2009 R11 Update. 

If all else fails, try re-installing QuickBooks.  You can download the latest release for your version of QuickBooks from our QuickBooks Downloads page.  You can't use your 2009 licensing information to install 2010, so make sure to download the correct version and year for your license.  QuickBooks will usually remember your licensing information when you re-install it, but just to be on the safe side I'd copy it down before starting.  You can find it in Help > About Intuit QuickBooks…