My PC always runs well... and the primary reason is that I use it as a utility machine, not an experimental toy. In my years of experience - there is a direct correlation between the computers that always seem to have problems, and owners who love to download and install every game, tool, utility, toy, trial, betaware, freeware, and application that they stumble across. Not only does it slow down the machine - but makes it much more prone to hackers, viruses, etc. Installing and removing software can cause defragmentation (fancy term for inefficient hard disk use) and can fill the registry up with stuff that is often not removed (Windows "logo" applications are supposed to remove everything, including from the registry, but not everyone does, especially the freebies). Also I don't use "applets"... I spent years downloading all sorts of cute utilities that each have one little purpose - I gave up that habit - the hidden prices are not worth it). If you don't know what I'm talking about - good - don't worry.
*** My Philosophy ***
I use two PC's. My new one is purely a utility machine. I use it for photos, music, video, email, wordprocessing, spreadsheets, and a few reliable games that I play regularly. My old one is for experimenting - sort of a quarantine machine for stuff that I will only need once, or very infrequently. yes - I still download stuff, but I'm much pickier about it, and I only install unknown stuff on my "old" machine. My old machine it 100% toastable. I can reformat it, delete it, whatever... there is nothing on it that I need, ever. If it's important to me, it's been backed up to CD/DVD.
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Here are my suggestions for keeping my PC fast and clean. If you're a big gamer, and you install/remove new games all the time, this may not work for you. If you don't think you can subscribe to my philosophy, then just do the next step (backup your files) and go have a beer. If you continue, print this first
DISCLAIMER: If this makes sense to you, and you consider yourself an intermediate user... go for it. If you are a beginner computer user, or if this doesn't make sense, then I'd suggest you not proceed and just avoid downloading everything you see.
1) Backup your files!!! Get a CD/DVD burner. Burn a disk with all of your personal files that are important to you including:docs, pics, email, contacts, calendar, installs that you don't have the installation disks for - ie. downloaded from the web. Don't worry about "settings" - colors, fonts, program options. In the worse case scenario, you can recreate all this stuff, but if you lose your files you'll be bummed. Trust me - if you only worry about stuff you create - you'll do a better job of backing up regularly. Don't use a "backup" program... just copy files to a CD/DVD. It's much easier to verify that you have a valid backup.
2) Verify your backup - restore them (temporarily) to your old machine. This will help you verify that you have a valid backup.
3) If you use your PC for video, photos, music, etc... get a big hard drive. Use the one that came with the PC for Windows and applications, and the new drive for all of your content. This will keep your machine from slowing down over time and will make future backups much easier.
4) Rebuild your machine: Chances are that your new machine was filled with crud that the PC maker was paid to install. Chances are that you won't use most of it. So if you have the option to just install Windows - do that. If not - then after "rebuilding", immediately go into Add/Remove programs and remove everything you don't use. If you have the option to "reformat" your hard drive, do it when installing Windows.
5) Install a firewall and get connected to the internet. The one that comes with Windows is fine. If you're not sure, just proceed to the next step and let Windows Update do it for you.
6) Run "Windows Update" Get all the critical service packs and configure it to automatically download and update your machine with future updates. Do this before installing all of your software and content.
7) Install Anti-virus software. Make sure to update the signatures frequently (automatically is preferred).
8) Install the software that you use regularly. If you're not sure - DON'T install it, until you need it.
9) Restore your files. If you're short on disk space, just put the ones back that you use regularly. Put them on the second disk if you can, so that you don't mix content with applications. Don't worry if you only have one hard drive, but if you are a purist, use a second drive for your content.
That's it - you've got a clean box.
Now - toast that old machine, and give it a fresh start too. Basically, you're just starting all over, but if you can subscribe to my philosophy, your new PC will stay highly-tuned for a long, long time.