Windows:
1. ease of use
2. very popular
3. good looking interface (even classic style)
3. lots of documentation
4. lots of tech support when you need it
5. its been around for a long time so its had years of expierince to get good
6. very very supported by software and hardware
7. not much knowlege of computers is needed to use
8...more to come cant think right now, im tired
Linux:
1. powerful
2. very expandable (open source)
3. nice interface (if tweaked through the options to look nice, stock interface is ugly)
4. defaults with 4 working desktops that can easily be switched through
5. comes with many programs that do things you would have to pay for on windows (office style programs)
6. loaded with server tools and applications to run right out of the box. (better than that IIS crap)
7. comes with tools for developmental enviroments (programming and such)
8. its free and easy to install
9. dont need to be an administrator to be able to use the OS's good features that are common in use (downloading, and such)
10. lots of help for it, very large user group.
11. lots of tools out there to port windows programs
12. built in pop-up blocker with the os
i like windows more. but i think Linux has more plus's but is more for that advanced user, thus i perfer windows, though i have my own linux box from which i like to do work on every now and then.