Are you wishing to archive because you need to change the form so much that the xml structure will be changed which would then throw an error when an older version is opened? If that's the case I would assume that you published your form template directly to the form library. The best approach is to create a form library to hold versions of the form. Then what you do is publish your form as a "Site Content Type". Then in the form library that is currently hosting your form, go to library settings > advanced settings > allow management of content types (change to yes).
Then you can have multiple form templates in one library. Oh and another piece of advice is on the form library that you use to store the form templates (the form content types) enable versioning in the settings. That way if you publish a new version to overwrite an existing one and it didn't work out as expected you can quickly revert to the last working version.