Various causes for slowdown of Windows 7 PC
Slowing down of a PC is often due to the presence of viruses on it, but it is not the only possible cause. It may be that your hard disk is full or it needs to be defragmented. Here is a list of possible causes of slow your computer:
- Malware (viruses, spyware and company) is present on your computer.
- After several installations, your files are disorganized and the system takes time to find the files needed to launch such a program.
- Your hard drive is full.
- There are too many programs open at the same time that saturates your RAM or RAM itself is low for your typical usage. We wrote previously how much RAM a Windows 7 computer typically needs for running smoothly.
To see the number of programs running on your computer, you can view the process list. To do this, right click on the taskbar and click Task Manager. Then go to the Processes tab:

Previously, we have written several topics on virus, malwares etc. You might be interested to read those articles too:
Solution
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The best way to solve this problem is to perform a virus scan and spyware scan, defragmenting the hard disk of your Windows 7, disable unnecessary programs that launch at startup (use msconfig) and uninstall software to save space on your hard drive.
If none of these solutions works, the drastic method is to reinstall Windows (or use System Restore) .
It is also possible that one of your components begins to age, in this case it is best to send his PC for repair or replacement of specific parts.
To summarize
- The most common cause of the slowdown of a PC is the presence of malware and viruses.
- Defragmentation can improve the speed of your system.
- You must disable the useless programs that launch at startup.

The solution seems to be too short. There are many other reasons for the computer to be slow. May some updates are missing, windows update should be checked or may be too much of graphic items are used,like you can always disable aero effect and animated wallpaper or screensaver. You have mentioned about processes tab, but what if a normal user stops some essential processes like explorer.exe, the computer would crash,right?? How about republishing this post with a bit detail into these sort of things.
Agreed its short. A book can be written on the topic.
The obvious reasons to run slow (underpowered PC, improper allocation and usage of programs etc.) are not taken in to account. Its obvious if a person runs x64 version of Windows 7 with 1 GB RAM, no dedicated Graphics Card yet uses a huge size photo as wallpaper and tries to run Adobe Photoshop, it will run slow, may be it will hang.
Actually stopping explorer.exe is not dangerous. The user can relaunch explorer.exe by running it again (File > New Task) from Task Manager. Its frequently done by the Theme creators to avoid the delay by the restart / log off – log on process. You can see this screenshot its taken right now – explorer.exe is off, I am browsing an exe to run a program – http://thecustomizewindows.com/wp-content/uploads/2012/07/sshot-51.png.
Thanks for the proposal for re-writing.