Upgrade standalone Lightroom 5.2 to 5.3 fails

Hello,

I have standalone LightRoom 5.2 installed (together with standalond Photoshop CS6).

I'm trying to upgrade to 5.3 after the standalone download but I get the same error as I've read in the forum during an upgrade via CC.

The message about a missing resource on a network resource shows up everytime.

It points to the 'Adobe_Lightroom_x64.msi' in a non-existent folder that looks like a registry key ( like i.e.: C:\Users\user\AppData\Local\Temp\{B6AE23A1-164E-4A00-A62D-75A9782F4B1E}).

When I point to the "real" folder where the file is located in then after a while the installers says that this installation file is not valid for LightRoom 5.2...

It also says that OLDER version 5.3 can not be removed (????)

However I'm installing 5.3. 

I don't get it and this looks as a big mix-up...

Can you please help me find the solution to this?

If the solution is to uninstall 5.2 first then I want to be sure that all settings and catalogs are retained...

Thanks a lot for your help....

Karel Claessens