Just to follow up China from China (gotta help a brotha out) :glasses1:
I have two computers; a 1.3gHz Athlon that's about 5 years old, and a Compaq laptop that's about a year old.
For the best performance, I would suggest the following programs be on your computer:
At least two spyware programs. I use Ad-aware and Spybot Search-n-destroy. Both are free downloads (you can find them easily with Google) and run a scan of your computer with both at least once a week. Always be sure to update the programs' definition files, as they are always adding new files that people create.
Have a decent anti-virus program running at all times, and always make sure your definition files are up to date. If you want free, AVG and is excellent and is available for free download. In order of programs where you pay, I would probably go in this order, from best to worst. ZoneAlarm Suite, Norton, McAfee, Trend Pc-Cillin. Again, scan for viruses once a week - I always just set it before I shower or something, and it's usually done by the time I get back.
Additionally, install a good firewall program, to block access of your computer from outside sources. This will significantly cut down on the number of spywares that enter your computer, and also give you far stronger protection against hackers. ZoneAlarm basic is a good, free program to do this. For me though, I have used both ZoneAlarm Suite and Norton SystemWorks, which combine both the firewall and the anti-viral protection into one nice program - currently I use ZA Suite, and haven't had a virus since I bought my computers.
Defragment your hard drive at least twice a week. The version that comes with Windows isn't very good, but there are some better ones out there which sort your programs in order of your use, so it helps speed up your file access. I use Diskeeper (you can get a free trial from the net), and it's about 3 or 4 times faster than using the one that comes with Windows.
Go into your internet settings in your browser and make sure the cache size is set to less than 50mB. You can find guides for this on thenet, depending on which broswer you use. As well, if you are using IE, make sure to run the Disk Cleanup program included with your Windows files (usually in Programs -> Accessories -> System Tools) once a week to help flush out any extra temporary files that may not have been erased from your computer. In Firefox, you can change the cache by going to Tools -> Options and selecting the 'Advanced' tab.
Uninstall any old programs or games that you don't use anymore. Backup photos and program setup files to DVD, CD or floppy, to ensure you have extra copies. Delete unnecessary icons from your desktop and startup menu, and try and keep your desktop wallpaper off (just set it to a nice colour). You should strive to have at least 20 % of your hard drive space free, and for best performance, usually about 33% or more.
Personally, I format my computer twice a year and start from scratch. It keeps things running smoothly and keeps buried files from resonating on my hard drive forever. I also sort everything very specifically; my root drive only has 4 folders: documents & settings, games, program files, and windows. My start menu only has 6 menus, and I delete any icon I don't need; my desktop only has the recycle bin (I have the other icons, one for each drive, and the programs I use the most, in the taskbar). I have two hard drives, and on the second one is where I keep my documents and music, while the first only has Windows and my programs. I back up all of my critical documents (photos, documents, phone numbers, fonts, wallpapers, etc.) once every few weeks onto DVD, and I keep all my setup files on one easy DVD, so I never lose them and always have them in one easy-to-reach place when I reinstall everything.
With a little care and diligence, my older computer runs at 110% of operating speed for my class of computers when I get it tested. When I worked at an electronics store, I was amazed at how many people never took care of their computer, and why they were always acting so slowly, when all it takes is a few free programs and a little bit of preparation and effort. Luckily for me, because they couldn't take 15 minutes out of their week to do it, I became several hundred dollars richer doing it for them.