The study on the Indian banking sector, conducted by Ascentius Consulting on behalf of Microsoft, said penetration of Windows XP in the sector is as high 70 percent.
"Some 34,115 Indian PSU bank branches are at risk, thanks to their reliance on Windows XP. Windows XP will no longer be supported by Microsoft, beginning April 8, 2014, but the study shows that the penetration of Windows XP in the banking sector is still high at 40-70 percent," Microsoft said in a release.
Amongst the greatest risks facing banks that maintain their Windows XP installations, despite the end of support, are their ability to respond to customers and manage waiting times, it added.
"The fiscal impact of this could be as much as a loss of business opportunity worth Rs 1,100 crore in a day and a loss of income worth Rs 330 crore over a period of 3 days (assuming that a major incident may take 3 days for the systems to come up to normal functioning)," the study said.
A large number of branches that rely on XP, especially in the rural and semi-urban areas may go down and therefore completely "deny service" to customers, it said.
In metro and urban branches, the impact may be as great as 55 percent of customers face an extended waiting time of up to 30 minutes for an average transaction.
According to a recent Microsoft security intelligence report, XP users are 6 times more likely to be infected than users of modern operating systems like Windows 8.1, despite encountering same amount of threats. XP users are also 21 times more vulnerable.
Microsoft further said that as per a study by research firm IDC in India, companies are prone to spend three times more if they do not put a planned migration strategy in place from the outset.