When installing Instacal on a machine running Windows XP, you receive a message stating "16 Bit Subsystem Error".
Problem
One or more Windows XP system files (command.com, autoexec.nt, config.nt) is missing or corrupt.
Solution
Download and Install XP_Fix.exe. This installation program will reinstall the missing or corrupt Windows XP system files command.com, autoexec.nt and config.nt. The absence or corruption of one or more of these files causes a "16 Bit Subsystem" error.
To download the file, please click HERE. (Please note that this program is written by a third party and is not supported by WHE Inc. You can learn more about this product by visiting the Visual Tour Website.)
After running the repair utility, reboot your computer.
You can read more about this issue at the following link on the Microsoft website...