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From the technical point of view there are three types of caches in Windows 7 which you can flush easily – Memory Cache, DNS Cache, and Thumbnails Cache. Clearing the Memory Cache can free up some system memory, clearing the Thumbnail Cache can free up space in your hard disk, and clearing the DNS Cache can fix your internet connection problem.
You can also clear Internet Explorer 8 Cache, but it not part of Windows 7 by default(atleast in Europe).
Clearing DNS Cache
Type Command Prompt in Start Search, right-click on Command Prompt under Programs and select Run As Administrator.
Now in Command Prompt window type ipconfig /flushdns and hit Enter.
As you can see from the screenshot above, it will show a message that the DNS Resolver Cache has been successfully flushed.
Clearing Memory Cache
When your computer is running for quite some time, you will notice that it slows down due to idle processes. You can use this method to free up unused RAM and speed up your computer. It requires you to create a desktop shortcut and then open it to clear the memory cache.
First right-click anywhere on the desktop and select New > Shortcut.
Now enter the following line when asked for location of the shortcut and hit Next:
%windir%\system32\rundll32.exe advapi32.dll,ProcessIdleTasks
Give it any name and hit Finish.
Now open this newly created shortcut and you will notice a slightly better performance
How To Delete The Thumbnail Cache In Windows 7:
The Thumbnail feature is no doubt very useful, however it also consumes some resources in terms of disk space. In Windows 7 Thumbnail cache are created so that the thumbnails in taskbar can be previewed much more faster. But if your hard drive space is very low, you may need to clear the thumbnail cache. This can be done by following these simple steps.
First of all, click Start, type Disk Cleanup and press Enter.
Then wait for a while, the program will scan useless files.
Now, locate and check the Thumbnails option, once done click Ok.
Now confirm the delete process in the next step by clicking the Delete Files button.
This will clear the thumbnail cache. Its that easy. Enjoy!