Welcome to the windows world casanova. This is what you get for using the most insecure and bug ridden os ever.
What I advise you at this point is .. challenge them at their own games. Tell them to show you the ip, and the server logs. Tell them that you would like them to come to your place and examine the pc by
certified professional. Just use some hi-fi words, like MCSE and MCSD certified professional and all, and I am sure the stinking ba*tards will not file an FIR. A company which provides service has no right at all to file a complaint against its consumer. In fact, even use the press -- I am sure they will bash TATA and be on your side. Call up TOI and Indian Express with what you have to say -- start a
War by Media.
Best of luck, and use Linux in the future ..