1. A Cluttered Registry
The longer you use Windows, the more cluttered your registry can grow, especially if you regularly install and uninstall software. Some applications, known as "orphan" registry entries, don't remove all traces of themselves when uninstalled, causing problems such as sluggish performance, system lockups, or a bloated registry that takes longer to load. The easiest way to clean your registry is to use a registry cleaner, such as PC Tune-Up. With the click of a button, PC Tune-Up will scan your registry for these fragmented files, bring them together, and safely remove them. This is what most geeks advise.
Personally, I do advise caution here: Unless you know what you are doing, even with Registry Cleaner programs, damage can de done here. I have personally encountered that and lost vital links, so-called “DLLs” and my operating program ceased working.
2. Full Hard Drive
It is possible that your hard drive might actually be too full of data to function properly and efficiently. You should have at least 2 - 3MB of free space for programs to run smoothly. If you don't have this much free space, you can delete unused programs on the C: drive. Check your C: drive to see how much space you have on your computer. You can do this by going to Start > My Computer > C: drive. Click on the C: drive and it will tell you how much free space you have under 'Details' on the left bar.
To delete a program that is unused and that you are hardly going to use again you must use the uninstall function of the program itself (if it has one) of uninstall the program via the “Add/Remove” section in “Control Panel”.
Also, often defragmenting the hard drive, generally the C-drive, of you PC can speed the operations of the PC up to some degree. This is because defragmenting brings together the fragments of programs and files that are often scattered all over the hard disc. Windows – and it appears that Windows is the only operating system – but I could be mistaken – that is plagued by this fragmentation problem – has a built in utility to defragment the hard drive under system tools and it is advisable to check on this every now and then. Windows XP will test the drive when initiated to “defragment” as to whether or not the drive does need defragmenting. Older Windows programs, which are no longer supported, such as WIN 9x, and WIN 2000 did not have that check facility and you had/have to use your own judgement as to defragment or not.
3. Not Enough Memory
It's important to have enough memory on your computer to keep programs running smoothly, especially if you have large programs, or play a lot of PC games. It is recommended that you have at least 512MB on your PC, although at this point, 1GB seems to be the sweet spot. The amount of RAM your PC has can be checked by right-clicking 'My Computer' and choosing 'Properties'. If you need to upgrade your RAM, be sure to check your local retail ads for sales. You can usually get a RAM upgrade at a great price.
There are still people who have, like me, less than that on my machines. Linux works sweet with less than that in RAM and all its components but on Windows this seems to become a problem. Why, on the other hand, beats me. Why do programs get more and more bloated and still do not do much more than their older cousins, is a very valid question, methinks. Sometimes one could wonder whether the is a conspiracy going on between hardware and software makers.
Too Many Start-Up Programs
When you boot your computer, there are several programs that automatically start behind the scenes. These programs eat up your computer's available processing capacity and slow it down dramatically. Most likely, you don't need all of these programs to automatically start when you boot your computer. Here you can get dedicated programs to remove such unwanted programs from your startup but I sometimes wonder whether that is all really worth it.
Spyware and Malicious Programs
If you have ever experienced annoyances such as a new toolbar in your Internet browser, or a new startup page that you did not set, you are likely plagued with spyware.
This is where the need for anti-virus and anti-spyware software comes in. You do not need to go and spend lots of money on such programs; many can be had for free that work as well if not better than their paid-for cousins. (Article on that subject to follow).