Why does my computer run fast after a clean install?

I recently formatted and reinstalled Windows on my laptop. It now runs much faster. I have been doing this about once a year for the past decade. Why is this needed?

I always figured this had to do with installing and removing programs, which over time fill up the registry with junk. Is this true? Are there any programs that can tweak the system without reformatting?

Solution 1:

The registry is a bit of a misconception, The way it works, it could be filled with junk but it shouldn't slow down your machine - imagine, all roads are linked, but just because there is a traffic jam somewhere doesn't always mean it will affect you somewhere completely different!

It is pretty much just software that starts with your computer, updaters and bad drivers.

You can greatly speed up your computer using Microsoft / Sysinternals AutoRuns and delete/disable enries you do not want to start up with your machine.

Solution 2:

• You try out lots of applications
  • Due to you computer's configuration, Windows loads in more junk than on a clean install.
  • Software developers believe their apps are so vital that
    • part of them must be loaded at boot time and have icons in the system notification area.
    • they need a special driver (but no one tries to write small drivers any more)
    • they should check something every 5s even if it only changes every 3 weeks
      • availability of updates _Wil
      • screen orientation
      • attachment of a phone etc
      • new files appearing that need indexing, adding to albums ...
  • Software developers tend to have the latest Mega-PC, and believe you should too.
    • So people with "slow" PCs should fix any problems by buying a new PC for the app.
• viruses, trojans, etc
• anti-viruses, anti-trojans, etc

P.S. I'm a software developer.