Tally 7 is not made for windows 7 so windows 7 is not supporting Tally 7. Tally 7.2 has been designed to run only on windows xp. But there are possibility with some additional downloads and softwares to run Tally 7 on Windows 7
By Using Windows 7 Virtual XP Mode To Run Incompatible Applications you can run tally 7 on windows 7.
Download and install Windows Virtual Machine for Windows 7 - Windows6.1-KB958559-x86.msu
Download and install Windows XP virtual machine - VirtualWindowsXP_32_en-us.msi
Once virtual machine is setup, install the application on guest OS (Windows XP) as shown below (Tally).