I have windows xp and it has started responding very slowly, so was thinking if the various software I've installed might be affecting its speed. PS: Even if I run one program/software at a time the same thing happens
Yes, the more number of programs, the slower is the windows by nature. You may not be running all the programs, but programs by themselves can run some services or processes to have them updated and can consume memory, which can result in slow down of system.
No, the speed of your PC is the same no matter what is installed, but the number of programs installed does affect the performance of your PC. Malfunctioning hardware can also cause performance issues. I would start by reviewing your installed programs (Control Panel) and removing what you don't really need.
Also, Windows XP is no longer supported by the vendor (Microsoft). You may want to consider upgrading to a more current OS (i.e., Windows 7).
There can be many reasons for this:
Many programs you install start some kind of background process when the computer is started. These all take a tiny toll on the performance of the computer, both CPU and working memory; when it sums up, it could be significant enough to feel it as a performance degradation. And you cannot see that these background processes are running. They often, though, but not always, add a tiny icon in the System Tray in the lower right of the screen. Each of those icons are connected to at least one background process running all the time. But there are many more background processes that you cannot see. Press Ctrl+Shift+Esc to get the Task Manager. Switch to the Processes view. Click the CPU column header twice so it sorts by CPU usage, highest first. Then you can see the processes that use most CPU. Sometimes a process can even be a runaway process that uses lots of CPU. Try ending that process if it keeps using lots of CPU and see if it helps; that can help diagnose the problem.
When you install programs and in general use the computer, the disk becomes more fragmented. This slows down the performance. Defragmenting the hard disk can help with that.
When you install programs, you get less free disk space. The less free disk space, the slower Windows gets; it gets harder for Windows to find the empty space it needs for temporary files etc. So be sure to keep a lot of free space on your disk. Remove anything that you do not need. Move that data to external disks, for instance. And uninstall programs you really don't need.
Programs tend to get larger and larger for each new version. Mostly because functionality is added. Also, they tend to get functionality that requires more and more ressources (CPU and memory) from the computer. So just keeping your programs up to date slows down the performance of your computer over time. There is no real remedy for this, as programs get unsafe if you use old versions. For some programs, though, there are old versions that are still being updated with security patches. For instance, there is still the old and fast Opera 12 browser (I believe it is still being maintained with security patches, although I am not sure).
Programs also tend to get larger and larger in working memory (RAM) footprint for each new version; they require more RAM when running. This includes the background processes that you cannot see. And your computer has limited RAM. When your computer is out of RAM, it uses the harddisk instead. This slows down the computer extremely much. Press Ctrl+Shift+Esc to get Task manager. Switch to the Performance tab. There you can see the memory usage as a graph. Compare that to the total memory (RAM) your computer has. When it is getting close to the maximum, performance will fall considerably.
Programs such as Google Chrome use a lot of memory, and more and more for each tab that is open. Keep the number of open tabs in web browsers, especially Google Chrome, down to a minimum.
In general, my experience is that working memory running low is the most important reason for a computer system to be slow.
a. Adding more memory is of course the best solution to that. But sometimes this is not possible; there are upper limits to how much RAM a computer supports.
b. Removing memory hogs such as reducing the number of programs that start when you start the computer is another solution.
c. Upgrading to Windows 7 will give you the option of using ReadyBoost which can significantly improve the speed of a system with limited memory; also, you would get a more secure system that is still being maintained with security patches.
d. Swapping your hard disk with a new and fast SSD could also make a significant improvement to the speed of your computer. Remember that there are fast and slow SSDs – find a fast one if you choose this path. But it does require copying (cloning) all the data from the old hard disk to the new SSD. Some SSDs come with a kit, software and instructions on how to do that. Remember to turn off any defragmentation programs after deploying the SSD; defragmentation is meaningless on an SSD and even shortens its life.
There can be many other reasons, but these are the ones that come to my mind, having had several slow computers over the years due to lack of funds – or, in case I had the funds, my lack of willingness to use them on buying a faster computer. :-)