More than one in 10 English health authorities recently polled can't say when they will switch away from the aged OS, raising the prospect of yet more costly custom support from Microsoft.
Microsoft may have ended support for Windows XP in April this year but the venerable operating system is still entrenched in corners of UK government.
The UK administration had to negotiate a deal with Microsoft to offer public bodies extended support for Windows XP earlier this year after it became clear that many authorities would be unable to migrate from the OS before updates ceased. At the time the deal was struck more than one million PCs were still running XP within authorities responsible for providing healthcare in England.
That extended support deal runs out in April next year, by which point public organisations are supposed to have replaced XP. But among healthcare bodies recently questioned, more than one in ten couldn't guarantee they would have moved from the OS before the government's extended support deal expires.
The revelation that some trusts may need support for XP beyond next April came in response to a Freedom of Information request submitted to National Health Service trusts by virtualisation technologies provider Citrix.
All of the 35 trusts that answered were still running Windows XP but 74 percent said they were planning to migrate their last PC from XP by March 2015. However, 14 percent of the trusts were unsure when they would transition their final machine.
The UK Department of Health did not comment on whether the government will seek to extend the support deal with Microsoft beyond April 2015 or how it will ensure trusts secure machines running XP after that time.
When the extended support deal was announced the UK government told NHS trusts it was vital they hit the April deadline.
"It is important to note that there are no plans to negotiate a further national extension of XP support beyond April 2015. It is therefore essential that all NHS organisations put in place robust plans to migrate away from Windows XP, Office 2003 and Exchange 2003 by that date if you have not already done so," it stated in a letter sent to trusts at the time.
A Department of Health spokesperson said it continues to remind trusts of the need to migrate from the OS.
"Trusts are responsible for updating their IT systems and we have recently written to them about the need to migrate away from XP and to put in place alternative arrangements before April 2015," he said.
Operating a long term custom support deal with Microsoft is costly for a large organisation - with the ballpark figure of $200 per PC for the first 12 months, $500 for the second 12 months, and $1,000 for the third 12 months being reported.
There are additional steps organisations can take to protect systems still running XP, such as restricting network connectivity, the apps that can be run, removing admin rights and barring browsing and email. Offering XP as a virtual desktop can also make lessen the burden of the additional monitoring and management needed to make the OS more secure.
There are also a number of third-party companies that will monitor Windows XP for vulnerabilities and issue patches as part of custom-support deals.