Security Issues

Windows XP has been criticized for its susceptibility to malware, viruses, trojan horses, and worms. Security issues are compounded by the fact that users of the Home edition, by default, receive an administrator account that provides unrestricted access to the underpinnings of the system. If the administrator's account is broken into, there is no limit to the control that can be asserted over the compromised PC.
Windows, with its large market share, has historically been a tempting target for virus creators. Security holes are often invisible until they are exploited, making preemptive action difficult. Microsoft has stated that the release of patches to fix security holes is often what causes the spread of exploits against those very same holes, as crackers figured out what problems the patches fixed, and then launch attacks against unpatched systems.


Crippled Functionality

In an effort to slow down the rate at which malicious programs can spread to uninfected computers, Service Pack 2 lowered the limit on outgoing TCP/IP connection attempts from 65,535 to 10.There can be no more than this many incomplete outgoing connections being attempted at any one time; additional connection attempts will be queued. This limit can adversely affect legitimate software such as peer-to-peer applications. The "tcpip.sys" system file can be patched to raise the limit to its former value.


User Interface and Performance

Critics have claimed that the default Windows XP user interface (Luna) adds visual clutter and wastes screen space while offering no new functionality and running more slowly – with some even calling it 'the Fisher-Price interface'. Users who do not like the new interface can easily switch back to the Windows Classic theme.


Backward Compatibility

Some users switching from Windows 9x to XP disliked its lack of DOS support. Although XP comes with the ability to run programs in Program Compatibility Mode, as well as a command program which is more like a 9x "Dos Box" than CMD, XP still has trouble running many old DOS programs. This is largely due to the fact that it is NT-based and does not use DOS as a base OS. There are open source solutions such as DOSBox and FreeDOS, though in a few cases an MS-DOS environment may still be required in order to run such legacy applications.