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 in Europe.
Clearing DNS Cache
Type Command Prompt in Start Search, right-click on Command Prompt under Programs and select Run As Administrator.
Now, 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:
Give it any name and hit Finish.
Now open this newly created shortcut and you will notice a slightly better performance.
Clearing Thumbnails Cache
In order to clear thumbnail cache, right-click your primary disk partition (where Windows is installed) and open Properties dialog. Now, click Disk Cleanup to open Disk Cleanup dialog. Select the items you want to remove, along with Thumbnails to remove the thumbnail cache. Once done, Click OK followed by Delete files to delete selected items and remove thumbnail cache. We have covered this topic in full details here.