For Uninstalling/Reinstalling FSX/Acceleration (boxed version), recommend the guide at the following link - https://support.precisionmanuals.com/kb/a87/how-to-uninstall-and-reinstall-fsx.aspx.
When reinstalling, you may get a 1722 and/or 1603 error. When you complete the installation of FSX, the 1722 error may popup. Click okay and the 1603 error will show up. When you click okay for the 1603 error, Windows will roll back the installation and you will have to reinstall FSX again. The following provides instructions for fixing these errors:
Click on the search bar and type Run and open up the Run command. Type regedit. This will open up the System Registry. Expand your registry keys to the following registry key -
HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\CONTROL\CLASS\{4D36E967-E325-11CE-BFC1-08002BE10318}
Double-click Upperfilters on the right side.
Change the value from 0 to PartMgr, and then click OK. (please spell PartMgr properly - case sensitive). PartMgr may already be the value and no change is required if this occurs.
Close Registry Editor.
Install the Software Licensing System Reset Tool package:
Go to the following link and click on the link "Download the Software Licensing System Reset Tool package now" - https://support.microsoft.com/en-us/help/928080/error-1722-when-reinstalling-flight-simulator-x.
Follow the Microsoft instructions for installing this package.
Reinstall FSX. There should be no errors at the end of the installation. Run FSX and enter your Activation License. If successful, close FSX and install Acceleration or SP2. If you install Acceleration, it will also install SP1. If you do not have Acceleration, you should download and install SP1 and SP2. Recommend you conduct a search on the Internet for SP1 FSX and SP2 FSX as links become non-existent over time.