Hi Jozef,
Which .Net Framework to choose would be very dependent on the target client PCs.
If most of your client is still on Win XP, then your safest bet is .NetFramework 2.0 - 3.5
.Net Framework 4 can target XP SP3+Vista+ Win 7
.Net Framework 4.5 can only target Vista + Win 7
For the Target Platform, refer to this table by Pedro Magueija in Error Retrieving the COM class factory for component with CLSID {XXXX} failed due to the following error: 80000003
Regards
Edy