The installation file is infected with virus
In the process of trying to download the TallyDeveloper installation file (TallyDeveloperSetup.exe) from the website, the anti-virus software (NOD32, etc) displays a virus alert message stating that the installation file is infected with a virus.
It can be due to false alarms from the anti-virus software or due to the virus infected in your machine.
You can send the TallyDeveloperSetup.exe file to your anti-virus vendors for a confirmation.