Games, security software and popular business programs are clashing with Microsoft's long-awaited security update for Windows XP.
Since SP2 was released to business users, reports have circulated about programs behaving differently once the upgrade is in place.
Microsoft has drawn up a long list of programs that do not sit well with SP2.
Included in the list are games such as Unreal Tournament, Photoshop Elements and most file-sharing programs.
Service Pack 2 for Windows XP is intended to make the operating system much less susceptible to the viruses, hack attacks and worms that have made the headlines over the last few years.
As well as giving users a single place to manage their anti-virus software, firewall and updates to Windows, the SP2 update also makes changes under the hood in an attempt to stop viruses and malicious hack attacks taking hold.
Early reports suggested that some of the changes SP2 introduced caused problems with programs that needed remote access across networks.
Now, about a week after SP2 was released to business customers, Microsoft has compiled a long list of programs that the update is known to cause problems with.
Microsoft has put together two articles detailing the problems. One deals with programs that behave differently after installing SP2 and a second that details the programs that seem to stop working after the upgrade is in place.
Many games, such as Unreal Tournament 2003 and Sim City 4, will behave differently because the firewall in XP is automatically turned on when SP2 is installed.
Paul Randle, head of all things XP at Microsoft in the UK, said most of the problems were caused by older programs that expected to have net access that the update shut off. They are also ones that are trying to communicate across a network between a client and a server.
Microsoft has produced guidelines for what to do if programs stop working after SP2 is downloaded and installed.
Many anti-virus programs from security firms such as Symantec feature on this list.
Mr Randle said updating anti-virus software with the latest versions should iron out the conflicts.
For some programs the list of instructions involves finding and opening ports used by programs to make sure they can communicate via the web.
For average users, these instructions could prove formidably complicated.
A version of the SP2 update for consumer PCs is expected to be released soon.
From BBC News