Step away from the puter, and take a deep breath... put yourself in a happy place...
OK now lets try this again (BTW I use Win 7 and I have no problems so this is just some minor annoyance which we will fix up post haste....) OK, there are a couple of things you can try, the first and probably easiest is to right click on the Icon, and select "Open File Location", you will see the X3 Folder and the X3TC.exe or X3Reunion.exe file will be highlighted, now Right Click on that and from the new context menu select "Properties". When the Properties page opens up select the second tab - "Compatibility", now look to the bottom - the section titled "Privilege Level" and add a check mark to the box beside "Run this program as an Administrator", click OK and ry again.
I have found that even if you are logged in with an account that has Admin privileges UAC will still block many programs that are in the Program Files Folder, so the above is recommended, and it has worked for me.
The other option which is a little more of a PITA, is to remove the game and reinstall but this time install it in any folder outside the C:\Program Files folder, I have used a second hard drive for some of my programs so what it looks like is this - E:\Program Files\Ergosoft\X3 Terran Conflict . Either method should work but the second will bypass UCA and is probably the better method overall.
If the above does not work let me know by posting back here or sending me a PM I am sure I can help you figure out some way to make it work. besides we need the help out there in the XUniverse there are allot of nasties out there...