Time to take a look at Windows from a Linux user point of view.
Let's start with the installation. You boot from a Windows XP CD and text mode installer pops up. The installer cannot find a a usable partition. Alas, all space of the hard disk is in use by Linux partitions. The Windows installer has no functionality to reduce a partition in size. How pathetic.
So you try to reboot to Linux, but you are unable to, but because the Windows CD has overwritten the master boot record. What nonsense is this? You did just boot the Windows installation CD without giving it permission to change anything. Why does it make my computer unbootable. Shouldn't one sue Microsoft for making computers unusable?
Anyway, you don't bother because Linux vendors have long ago adressed this problem. You insert your Linux installation CD, select "boot installed system" and when your Linux installation has booted run Lilo to fix the master boot record. You shrink one of you partitions to make space for Windows and boot the Windows installation CD again.
This time the Windows installer is able to find free space to create a partition and start the installer. After a short while the installer becomes graphical, displays some nice looking screens and about an hour later the system has been installed. Obviously your master boot record is gone again. Windows appear to have a boot manager to boot multiple operating systems, but it appears it cannot boot Linux. How's that possible in the 21st century?
So you fix your master boot record again using your Linux installation CD and move on with Windows. There are quite a few problems with the system as installed. Windows has put the system in a low resultion and terrible refresh rate. You think you may need a driver, but the installer has not made your ethernet interface functional either. You have to resort to the floppy disks of the 80's to get an ethernet driver on the system.
Talking about drivers, why do I need to do all this shit? My Linux installation CD was able to deliver the system in a "ready for use" state. Why is Windows unable to do so? Where do I find drivers. You ask a Windows expert and he says you need to go to the website of the chipset manufacturer of your video card, sound card, ethernet chipset and so on. How do I know what is the chipset manufacturer of my hardware? Windows is unable to tell you.
So, you boot to Linux, execute an "lspci" and you have a list of all devices in your system. Armed with this information you boot back to Windows and are able to visit the website of each chipset manufacturer and download drivers. While you install them, some video driver tells you need to download .NET to make it work. What nonsense is that, downloading large codebases to get your hardware working?! So, you spend another and half an hour waiting for the .NET download to complete.
Next a "Windows update" round, which takes another 1,5 hours.
If you are lucky, after about half a day, you have a system that is somewhat in an usable state,.
The operating system has some kind of start menu that changes all the time so you never find the application you want to use, so you end up clicking on the "All programs" option all the time. Because that is too much work Windows allows you to create "icons" on the desktop so you can launch your favourite programs easily.
Unfortunately the desktop often hidden under a few Windows and your desktop quickly gets overcrowded. Windows also annoys you with some kind of "thinking menu's" where many usefull features are hidden. The user interface also suffer from a problem that is called Bobification in the Windows world, the software vendor has confused user friendliness with talking dogs, annoying text balloons etc. Some of these Bobifications can be switched off, other cannot and keep annoying you.
Windows is, even today, anno 2008 not capable of accessing Linux partitions. That means one cannot access his documents on the Linux partition. You can boot to Linux and copy the files to the Windows partition, but you quickly encounter the problem that the Windows Notepad is not capable of displaying files with Unix line-breaks. Such a bug, which is meanwhile present for two decades in this program
The web browser included isn't very comfortable. For example, the middle mouse to open a link in a new Window doesn't work, the browser does not have any popup block, spelling checker. Support for modern standards like SVG , xhtml or html 5 is missing, just as well as support for more recent CSS standards. Also it has the strange habbit to redirect incorrectly typed URL's to Microsoft's search service rather than giving a helpfull error message. It's privacy features are weak: It tries to remind passwords without asking permission for that, it offers few options to remove privacy sensitive data, offers little options to control cookies.
The included e-mail client almost forces me reply to e-mail in a nettiquette incompliant way. It's IMAP support is really slow and supports very little of the IMAP standard, you can't really use it well for my mail folders. The anti-spam options are pathetic. Must-have features like an option to show all e-mail headers, a bounce-button, the abiity to set usefull headers like Reply-To are totally absent.
The Windows command-line is terrible. Copy-pasting for example cannot be done with mouse selection, it must first be requested from the context menu. Essential commands, like equivalents for test, for, find, grep, tr and so on do not exist. Some of the missing functionality like finding files can be done with the GUI, but doing anything with it is not possible. It is also very hard to find (perhaps because it is such piece of crap?).
While Windows does allow one to access files on a Windows server, an SSH client to access files on a Unix server is absent, just well as an NFS client. A command-line ftp client is included with the OS is present, but it is so pathetic that one would pray not to have to use it. Unfortunately, ftp is often the most common sense to transfer the files to/from the Windows machine.
Windows is so unusable that you start to put lots of work into installing lots of third party utilities for its shortcoming. You install tools like WinSCP, Total Commander, Winrar, Irfanview, Putty to make your life somewhat bearable. Unfortunately this is again a lot of work, and also, many of these tools do not come for free. Many Windows users do not care anyway, because they pirate everything.
Windows does not come with a package management system. This means that installers cannot automatically requisites for a program automatically, it is up to the user to find them. This also means the system cannot clean up unused middleware automatically.
Some custom installers do allow testing the integrity of the installed files, many do not. Even if it is possible, this functionality is often not automatable to system administrators cannot automatically check for errors in the installation of programs.
Scripting common maintanance tasks is very hard, because most tasks need to be performed using the GUI, causing a lot of handwork in administrating the system. Many settings can be configured using the GUI in either the control panel or "system console", but many usefull setting are inaccessible through the GUI. In such case one much make the setting through the incomprehensible registry. The registry is so uncomprehensible that it is very hard to find incorrect settings in it, and also keep track what various programs change in it. One must hope that the programs do their job well, because once there is an error in the registry it is very hard to find and solve the error.
Windows is unable to give any convincing alternative as a desktop OS, wether looking at installation, usability, or maintenance. Many essential functionality is missing, otherwise functionality is present in a very primitive way that no professional user wants to use. There is even functionaility that is outright annoying. The security issues haven't even been discussed yet, as a Windows user depends on external tools to keep his computer clean from malware like virusses, trojans, adware, and spam botnets.
For a professional computer user, Windows can only be regarded a toy OS. Because Windows is good for playing games, and other forms of entertainment on the computer.