Multi currency once turned on can not be turned off
and as far as I know once you set the home currency that can not be changed either
You have to purchase a 3rd party service to turn the multy-currency off.
I agree with Rustler, alex54.
In addition to what our Community Backers suggested, you can revert the multi-currency feature by restoring the back up you created before you turned it on. From there, we can change EURO to Dollar.
Before doing so, please create a back up again before making changes. Let me show you how to restore a back up file:
You can now work on with your new company file.
Let us now if you need more help with your company preferences.