Switch all users to utf8?

[hobox]

I have a board which used to have the regular swedish option. Now I switched the entire board to swedish-utf8 and removed the old language files. But somehow it seems that some of my old users still are on the old system because it shows up in the error logs on the apachewebserver that requests are still made to these files. How can I check and then without the users knowledge switch them over?

[SleePy]

hobox,

You can do a update on the smf_members table to the lngfile and set it to the new langauge.
You could as well disable user selectable languages.