Have never worked with Infoapth 2007 but in Infopath 2010, and I do not think it is different in 2007, editing of Infopath forms requires Infopath Designer (2010).

Otherwise, you can try to change XSN template source XML files though it is unnecessarily complicated way which I had never tried without using Infopath Designer. Besides, the Infopath form template schems of type /compatibility Workflow are locked and the results of such editing as well as packaging the changed source files back into XSN template archive are unpredictable and generally the worst approach from the limited set of available bad ones.

See also my answer to question:

• How to reconnect InfoPath task form to SPD workflow after moving it to the new Site Collection

Have never worked with Infoapth 2007 but in Infopath 2010, and I do not think it is different in 2007, editing of Infopath forms requires Infopath Designer (2010).

Otherwise, you can try to change XSN template source XML files though it is unnecessarily complicated way which I had never tried without using Infopath Designer. Besides, the Infopath form template schems of type /compatibility Workflow are locked and the results of such editing as well as packaging the changed source files back into XSN template archive are unpredictable and generally the worst approach from the limited set of available bad ones.

See also my answer to question:

• How to reconnect InfoPath task form to SPD workflow after moving it to the new Site Collection

Have never worked with Infoapth 2007 but in Infopath 2010, and I do not think it is different in 2007, editing of Infopath forms requires Infopath Designer (2010).

Otherwise, you can try to change XSN template source XML files though it is unnecessarily complicated way which I had never tried without using Infopath Designer

Have never worked with Infoapth 2007 but in Infopath 2010, and I do not think it is different in 2007, editing of Infopath forms requires Infopath Designer (2010).

Otherwise, you can try to change XSN template source XML files though it is unnecessarily complicated way which I had never tried without using Infopath Designer. Besides, the Infopath form template schems of type /compatibility Workflow are locked and the results of such editing as well as packaging the changed source files back into XSN template archive are unpredictable and generally the worst approach from the limited set of available bad ones.

See also my answer to question:

• How to reconnect InfoPath task form to SPD workflow after moving it to the new Site Collection