Windows Vista is causing problems for some new PC owners hooking up their machine to a broadband connection.
Some new PC owners have faced problems getting online
Some old installation discs that simplify the task of configuring a PC for broadband have refused to work on machines loaded with Vista.
One reader was warned by Virgin Media that it would be "weeks" before its software worked with Vista.
Other net service firms have also admitted that the appearance of Vista has caused some hiccups for users.
Microsoft launched the consumer versions of Windows Vista on 30 January and anyone buying a PC since that date is likely to have it installed on their brand new machine.
Many are thought to have suffered the same problem as Swansea-based Rob Evans who found that he could not use his existing Virgin Media account with his new PC from Tesco.
After ringing Virgin for help he was told that Vista support may not be forthcoming for some time.
A spokesman for Virgin Media, formerly NTL/Telewest, admitted that its discs did not yet work with Vista but added that Mr Evans was now using his broadband service.
"We can get people online without the installation disc," he added. "It's not that it does not work, it's just the disc."
The spokesman said that other net service firms were also known to be taking time to get to grips with Vista.
"It's such a big product that to train staff up on it fully and make sure all your services are tested and compliant takes time," he said.
Microsoft launched Windows Vista to consumers in January
A spokesman for BT said: "I think we are now supporting it though we did have some issues with it."
In particular, he said, Vista was conflicting with the Norton security software that BT sells with some of its broadband bundles.
"That's now been ironed out," he added.
The spokesman said BT had created a help page devoted to Vista to make it easier for people to get their PC connected.
Net service firm Tiscali advises its users to back-up important data on their Vista PC before attempting to connect it to broadband.
Andrew Ferguson, editor at Think Broadband, said: "I suspect Vista is going to break a lot of things as it makes some major changes to how things are done in Windows."
"Many places aren't up to speed with Vista yet," he said.