After years of use, I conclude with any windows operating system, it becomes slower over time, I notice that some virus checkers/Firewalls are making this even more painful.
Licencing issues and office/microsoft updates are also contributing to this, making using Microsoft, become painful and almost pointless for day to day stuff.
I have recently switched to (free) Ubuntu and am pleasantly surprised, the more I use this and its free apps (compatable office and email etc) the less I use MS, I also noted that dual booting I can always switch back if needed, I like the way Ubuntu imports your settings into its Operating system, and the way you can still view files in your Microsoft partition when you use dual boot.
I wont be switching back unless there are apps that wont run in Ubuntu.