IBM has told its army of PC users to hold off downloading and installing Windows XP Service Pack (SP) 2, released to manufacturing by Microsoft last week, until it has been fully tested and customized.

IBM cited known application problems and incompatibility with IBM workstation applications, noting Windows XP SP 2 causes a change in the behavior of Internet Explorer. The decision affects nearly 400,000 desktop PCs. IBM was unwilling to comment.

HP has also instructed its own users to delay the service pack’s installation. Ironically, HP’s web site details information for consumers and business users on how to install the patch.

An HP spokesperson said potential conflicts had been identified, adding it’s standard procedure for the IT department to test new software for compatibility before internal rollout.

[HP’s] not like a standard consumer downloading the software, the spokesperson said, noting HP had to ensure compatibility with, among other things, data centers.

Microsoft’s work on Windows XP SP2 was supposed to have been exhaustive and these delays will cause some embarrassment. The pack has been designed to close the desktop operating system to outside attack while also simplifying users’ administration of security. Changes included pop-up blocker, protection against e-mail attached viruses and reduced risk of buffer overruns.

Such has been the level of effort inside Microsoft, which is attempting to get Windows XP SP2 right on the first go, that the focus has pushed out the delivery timetable on other, related products. Two weeks ago, Microsoft said Windows Server 2003 for 64-bit Extended Systems, Windows XP 64-bit Edition for Extended System and Windows Server 2003 SP1 are all being pushed back to the first half of 2005 to provide greater resting with the server-based elements of the service pack.

Commenting on IBM’s delay, a Microsoft spokesperson said; What IBM is doing is prudent and we would expect any well run IT organization to do the same.