People talk a lot about ways to "speed up Windows" or keep your system well-maintained, but Windows has evolved a lot, and some of those are outdated. Even worse, some of them are just downright wrong, so here's our short list of the maintenance tools you do and don't want to run.
Maintenance You'll Want to Do
Update Windows: We've said it before, and we'll say it again: Don't neglect Windows Update. Install updates when it gets them, and restart your computer if necessary. This will keep your computer safe and stable, and really takes no effort on your part.
Run Antivirus Software: It's a sad fact of life, but if you're using Windows, you'll probably want some form of antivirus software running in the background. There's no need to pay for antivirus, though—Microsoft Security Essentials is pretty great on its own (Update: Microsoft Security Essentials isn't as good as it once was, so we now recommend using Avast). Of course, the best defense against malware is safe browsing, so the more responsible you are, the better off your computer will be—antivirus or no antivirus.
Back Up Your Hard Drive: Whether it's the simple Windows Backup or an automated, offsite backup tool like our favorite Crashplan, backups are essential tools for any PC user. It isn't maintenance, per se, but it can get you out of quite a few binds, so we can't recommend it enough.
Clean Temporary Files with CCleaner: Windows can leave a lot of clutter and temporary files lying around your hard drive, and it's a good idea to clean these up once in awhile. We've sung the praises of CCleaner many times before, and with good reason. Just set it up to run automatically on a schedule, and you'll keep your computer free of all the temporary clutter.
Uninstall Programs with Revo Uninstaller: Windows' Add/Remove Programs dialog is okay, but Revo Uninstaller is even better. Not only does it remove every trace of an application from your computer, but it also helps you uninstall apps you can't find, as well as manage your startup processes which will help you boot up faster and run smoother once you do.
Maintance You Don't Need to Do
Defragment Your Drive (Unless You're On Windows XP): One of the maintenance operations people always talk about is defragmenting your hard drive. Times have changed, however, and this isn't actually necessary. Windows Vista and 7 automatically defragment your drive, so there's no need to do it yourself. If you're on XP, however, you'll still want to defragment, and you can just set Disk Defragmenter to run on a schedule. Note that if you have a solid-state drive, you don't want to run Disk Defragmenter—whether you're on XP or not. SSD's don't need it (but they will need TRIM enabled).
Clean Your Registry: You've probably also heard about registry cleaners before, but the fact of the matter is that they probably won't do much to help your computer. They won't cause harm to your computer, but you're very unlikely to get any kind of results. Leave these ones alone.
Mess with Windows Prefetching: You may have seen a few articles around the net on cleaning out Windows' prefetching to speed up your computer, but it's pretty much a myth. Not only will you not see any performance gains, but you could actually cause more problems instead of solving them. Just leave prefetching alone; Windows has it there for a reason.
Regularly Reinstall Windows: Sometimes it's unavoidable, but as long as you're responsible about what you install, there's no reason you need to reinstall Windows every six months. Be careful about what you download, test new programs in a virtual machine, and run the maintenance tools we mentioned in section one, and you should be able to save yourself a few hours every month.
That's our short list of Windows maintenance tools, but it should get you started. We've gone through a much more detailed list of Windows maintenance tips, but these are pretty much the essentials here, so they should keep your computer running in tip-top shape for awhile. Check out our more detailed list for an in-depth look.
Thank you for the folks at http://lifehacker.com/ for this information.