Convert a 'Single Line' field to 'Drop Down' without data loss!

Convert a 'Single Line' field to 'Drop Down' without data loss!

Is this possible? When I try this I get an error message that says:


Warning: Data Loss Detected

All the records and report columns associated with the field will also be deleted. This action cannot be undone.

[I understand, Proceed]    [Cancel]


Thanks.