In general, you should install and update a good antivirus program, disconnect the pc from the network, restart in safe mode and run a full scan, but this kind of task should be done by your IT people, so I would recommend to let them know about the problem.
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Removing the virus of your Tally software program always needs a latest and updated antivirus software installed in your computer system. However, before concluding that your computer is infected by a certain virus, try to uninstall and install the Tally software again because there might be another problem like corrupted or error files.
Most of the time, viruses are designed to hide and imitate a file or folder in any storage device. Your Tally file might have been already converted to a shortcut file or hidden mode files. To solve this problem, perform a full system scan to your computer’s hard disk drive. Although it might take too long, the result would be beneficial for your important files.