Hello Thomas,

Please try following:
Download the Visual C++ 2013 installer available on following link (you need to download the x86 version also if the OS is 64bit):
https://www.microsoft.com/en-us/download/details.aspx?id=40784
In case this should not help try to use before this repair tool http://www.microsoft.com/en-us/download/details.aspx?id=30135 and then try again to start WebSite X5.

Please keep me updated.

IMPORTANT! If you are getting this Message: "Incomedia WebSite X5 Professional has stopped working" The following instructions may be the fix. It worked for me.

 If you ever installed Lavasoft Ad Aware and uninstalled it you most likely have leftover registry entries and files that need to be deleted before Websitex 13 will start.

1. Go to Start>Run and type Regedit and click OK
2. In registry editor go Edit>Find and type in Lavasoft then click Find Next 
3. Delete any entry that is named Lavasoft then click Find Next until it finishes the search then close the editor
4. Do a search for Lavasoft in Explorer to find any leftover files and delete them or rename with .old extention.
5. Restart Windows and try opening X5 v13

NOTE: These files in step 4 may not have anything to do with the start up of X5 but you don't need them.

Hope this helps!