You can have 2 way to solve the problem.
1. Uninstall Xin Invoice and re install again. Make sure you select Install Xin Invoice for everyone in Select Installation Folder windows like shown in below.
2. Do some changes to set Xin Invoice run as administrator
To do so,
go to C:/Program Files/Xin/Xin Invoice 2.0/ if you are using windows 32 bit or C:\Program Files (x86)\Xin\Xin Invoice if you are using windows 64 bit.
Right click on xininvoice.exe
Click on Properties
Click on Compatibility Mode
Make sure checkbox "Run this program as an Administrator" is checked.
Click on OK
Go to Open xininvoice again.
The problem should be solved.
If, the problem still there. Please send email to firstname.lastname@example.org