This just does not happen, this is nothing to do with SambaPOS. Probably your PC has a virus or are in a corporate environment where they have placed restrictions on what software can be used.
When you say “uninstalled”, can you actually check is SambaPOS still showing in Control Panel > Add & Remove Programs? Does the folder
C:\Program Files\SambaPOS4 (or
C:\Program Files (x86)\SambaPOS4 on 64bit systems) still exist? If it does, the program wasn’t uninstalled, just the icons got removed (which could possibly due to trying to install on a standard user (i.e. non admin) windows account.
There are ways in Windows where software use can be restricted, but not automatically uninstalled. So if you are linking to a server which can assume admin control over your system, there could be a group policy that would stop you running SambaPOS (and it may hide icons, I really don’t know I have never used this). There are also third party monitoring tools which can be quite hidden and they can block use of software (things like ActivTrak) but they will again just block use or hide/remove icons. You say you reinstalled Windows and it happened again so to me that would pretty much rule out all of that, and then leaves the potential for viruses or malware which could remain.
Does any staff use the system? Is it possible someone deliberately uninstalled SambaPOS when you were not there? I would say this would be the highest possibility.
You need to give more info, we can’t spend time on things not related to SambaPOS when you don’t give any further info. And again, this is not a SambaPOS issue.