Well I'm one of the those people who really need to perform regular maintenance on XP, it doesn't take much for my comp to feel the strain. I had to strip down my installation with nLite, those recovery disks HP gave me, or 'bloatware' as I like to call them, just terrible.
Anyway, there's some good info here especially for the novice user. I'm fairly skeptical when it comes to cleaning out Windows prefetch however, I've heard it can cause slow downs if you do it often, I had to uncheck the prefetch option in CleanUp! since I use that near enough every day, CCleaner has it unchecked by default I believe. I'm sure there's no harm in cleaning it out every few weeks though, along with a defrag.
Another thing that worries me is the use of registry cleaners, especially ones that automate the task for you. Personally, I use jv16 PowerTools and only delete things I'm absolutely sure are obsolete. Of course the biggest advice to give here is
always, ALWAYS, back up your registry before making changes to it, ignoring that is one of the main reasons I've had to do dozens of reformats in the past. I normally do a full registry backup after every clean install, it may be a good idea to have a seperate partion set aside for all your backed up files as well.
My biggest tips for keeping everything running smoothly would be...
Run regular virus/spyware scans I don't run anti-virus software, however I do use SUPERAntiSpyware pro, which includes real time protection against spyware, which for me is the biggest and most common threat, at least in my experience. Running a firewall, anti-spyware, and anti-virus at the same time will only take up valuable resources and lead to a slow startup time (I'm not advising anybody else to do the same as me, it's a good thing thing to be paranoid about security!) All my scanning is done either with that or by taking advantage of excellent online services such as the one provided by TrendMicro. Use a firewall too, I use XP's built in firewall (set to no exceptions) + a hardware based one, I'm perfectly happy with this combination.
Defragment your drive I tend to only run defrag when I feel the system could benefit from it the most, I've never schedueled for it to be run once a month, you
just know when the time comes. When things start to become unresponsive and you begin to hear constant noises from your HD where it's not coping with the strain, then it's time to do some major maintenance lol.
Disable unnecessary services and startup programs This should be one of the first things you do after a clean install. There's a lot of things that you really don't need running that Windows sets to run by default, use the 'BlackViper' and 'Sysinfo' links in my sig for great resources on your startup programs and services.
Cleanup before every last shutdown This includes emptying the Recycle Bin and deleting temp files and cookies. I use 'CleanUp!' to automate this task instead of CCleaner. (Just make sure the 'Prefetch' option is unchecked!)
Delete obsolete registry entries and run Chkdsk Don't take registry cleaning lightly, don't just go deleting entries willy nilly, and make sure you
back up regularly. Another thing you can do once in a while is check your hard drive for errors by running Chkdsk. To do this, double-click My Computer, right-click the drive you want to check and select properties, then tools, error-checking and check now. These two don't need to be performed too often, I tend to check the registry whenever I've installed/uninstalled a lot of programs and things, and Chkdsk is only really needed when you get a lot of errors within Windows or you hear your HD making peculiar sounds (lol)
That's about all I can think of at the moment, the first two things you should do in Safe Mode, that's what I do. At least unplug your internet whilst scanning for viruses/spyware, and you shouldn't have anything running whilst defragmenting, that's my advice anyway.
(Sorry, long post I know)
