
Hey There Scouse M'dear,
Your log looks clean to me

, although I would make a point of disabling Windows Messenger, it just leaves you open to popups. You can do it easily with
Shoot the Messenger.
Can you answer a few? Did the slowdown happen all of a sudden, or has it been steadily declining?
Are you sure that all of your updates and maintenance are done?
If not, that's where I would check next, make sure you are fully updated, run Defrag, CCleaner, and give RegSupremePro from my sig a try. I think if your problem is a bloated registry, the computer struggling with thousands of temp files, and a seriously fragmented HD you will get great results. If not, you will have everything in great shape for us to troubleshoot from there.
If you are all clean and pretty and up to date, then I would suspect some type of system file problem.
Looking forward to your reply,
TTFN
LGW