unable to uninstall XnViewMP ; files cannot be deleted

[cynflux]

I had installed the portable version of XnViewMP on a flash drive, but uninstalled it later on.
There are 2 files that cannot be deleted, no matter what i do.
They are as follow:

Invali.dat
erbirdpo.rta

Can anyone advise on how to delete these?

Thank you in advance.

[xnview]

these files are not from xnview mp

[cday]

these files are not from xnview mp

If the files can't be deleted, I suspect that they are related to some utility that was on the flash memory when it was new...

[cynflux]

Thanks for the responses.
I am re-formatting the flash drive to get rid of these files.
I've already backed up the rest of the data that was already on the drive.