Pinatubo wrote on Mar 13^th, 2014 at 12:51am:

Markoz wrote on Mar 12th, 2014 at 10:16am: ...I take it you can't do a repair by running the installer again and using a "repair" option? In my Window 7 Control Panel\Programs and features, when I right click on PXXG_MD11_FSX, I get the option to Uninstall or Change, when I select Change, I get he installer window (don't know what else to call it) open with 3 options - Modify, Repair, and Remove. Try the repair from that. Mark, Thanks for your answer. I did it several times (repair option), including installing and uninstalling FS and the add-on. No joy. :-/ I think the only solution to solve the problem is to format the new HDD, installing only W7, FSX and Kaspersky Internet Security, not copying any previous files, where must be a hidden bug due incorrect add-on uninstall, and giving a try to watch if FS is running well. If so (I hope), I will install all others programs including MS Office 2010 and adding their important files who are stored in an external HD. Nothing more. I'll keep my fingers crossed! ;) Please tell me what do you think. Thanks.

Formatting the drive will fix it.  My feelings are that file is writing to something in your registry and therefore interfering with FSX every time you attempt to install it.
I would go into the registry and removing anything from that company.
Then re-install FSX.

Only a guess so no guarantees.