These reports were confirmed by the hospital when it issued a terse media release on Tuesday afternoon.
In it, the hospital, one of the largest in Melbourne, said: "Melbourne Health would like to reassure all of our patients and community that there are minimal disruptions to patient services today (Tuesday).
"Elective surgery and our Emergency Department are operating as normal. There have been a very small number of outpatient cancellations.
"Our IT team are making good progress in rectifying the issue and we hope to be back to normal as soon as possible."
Whether the computers running Windows XP are the hospital's own or have been supplied by an outsourcer is not clear.
Windows XP was released by Microsoft in 2001 and, after numerous updates — including more than 800 fixes in August 2004 — was considered one of the stablest ever to emerge from the Redmond-based company.
Though there have been four releases since then — Windows Vista (2006), Windows 7 (2009), Windows 8 (2012) and Windows 10 (2015) — many companies and individuals have preferred to stay with what they feel is a known devil, given the susceptibility of Windows to viruses, worms and every kind of malware known to the IT industry.