One of the core principles of effective troubleshooting is that degradation in performance almost always has a proximate cause. Find that cause, reverse it, and you restore performance to its previous, acceptable level.
When trying to track down that elusive proximate cause, the most important thing you can do is ask a simple question: What changed?
When did the problem start? Did you install a new program, device, or driver? Did Windows or a third-party program update itself? Did you experience a power failure? If you can reliably say that your system was performing properly on Wednesday but began misbehaving on Thursday, you may be able to use System Restore to undo system-level changes. If that works, you can try to figure out what happened so that you can prevent it from happening again.
Two key principles to follow when troubleshooting:
- Stay alert. If you notice your computer slowing down or behaving in an out-of-the-ordinary way, investigate the cause as soon as possible. Don’t install any additional software or make any system changes until you’ve figured out the problem.
- Don’t automatically assume that the first or most obvious change you think of is the proximate cause of your problem. If you installed a patch via Windows Update, that may or may not be the cause of your current problems.
In the next two installments, I’ll explain how to use diagnostic tools to zero in on the precise problem.
Ed Bott 
Where is part 4&5 of the slow startup tips as promised?
I agree with Armand, how can someone write that they will explain the next steps of a tip”later in the week” and 5 months later not finish it?