we had similar questions with great answers and tips: How can I find out why my computer slows down? How can I fix a slow Windows XP computer?
The truth is, Windows slows down with time for many different reasons. You don’t have to answer all of the questions below, but they may reveal one or several causes for your lag.
Is this a desktop computer or a laptop? If laptop, what type of CPU? The CPU can slow down if it gets too hot. Hence you should make sure no dust blocks the fans of your computer.
What version of Windows are you using? When was the last time you reinstalled your computer? Do you continuously install and uninstall a lot of programs? These questions help us estimate whether a stuffed or messed up registry or fragmented hard drive could cause your lag. This is the most common cause for lag in Windows. You can easily defragment your hard drive and see whether it improves the responsiveness of your system. However, if the registry is to blame, I wouldn’t mess with it. The easiest and safest way to fix a bad registry, is to reinstall Windows. make sure you backup all your data!!! for backup tools check out this question: What are good backup programs?
How much space is left on your C: drive? If Windows does not have enough space to store temporary files, it becomes slow and unresponsive. You can free up space by emptying your trash, deleting temporary files, uninstalling programs you don’t need, and moving all your personal files. My recommendation: never store personal files on the same partition as your system!!! You can store your personal files on a secondary partition, an external hard drive, a USB flash drive, or burn them to a CD or DVD. To clear temporary data use CCleaner. This tool can also clean your registry, but I would not advise you to do it!
How much GB RAM (rapid access memory) do you have? If this is an older computer, but you’re running newer software, your RAM may be challenged and Windows has to use some of your hard drive to store memory. The hard drive, however, is much slower than the RAM, hence your computer becomes slow. Solution: either reduce number of running programs (see below) and/or upgrade your RAM.
What type of graphics card do you have? Does it have its own dedicated memory or does it used shared memory? Graphics card with shared memory put an extra burden on your RAM. so if you do anything that requires your graphics card to work (scrolling), while your RAM is already at max with running programs, you may experience lag.
To free RAM, you can start by reducing the number of running programs. Note that many programs set themselves up to boot with your computer. You may not notice that they are running, but they are eating CPU power and RAM. The easiest way is to go to > start > All Programs > Autostart (folder) and remove any programs that you don’t want to boot with Windows. However, not all programs that boot on startup are listed in this folder. To catch them all, go to > start > Run and type > msconfig in the text field, then click > OK. The system configuration windows will load. Switch to the > system start tab and uncheck the box for programs you don’t need. Be conservative, don’t uncheck everything. Ask Google if you don’t know what an element does or is good for. Check out the following article for some more tips and tricks: How to Speed Up Your Computer with Just one Double-Click
Finally, do you use anti-virus and anti-malware tools? could it be that your computer has been infected? Check out this question for some pointers on how to keep those nasty things away from your system: What is the best free anti-virus and anti-spyware software?
That’s all I can think of right now, but there certainly is more. Anyhow, we should have the most important points covered. Please do not hesitate to ask in case anything of the above is unclear or too vague! We will elaborate and explain in more detail if you ask.