Step 1: 

Open the Windows Control Panel and under Programs, select "Uninstall or change a Program". After that, click on "Android Studio" and press Uninstall

Step 2: 

To delete any remains of Android Studio setting files, in File Explorer, go to your user folder (%USERPROFILE%), and delete .android, .AndroidStudio and any analogous directories with versions on the end, i.e. .AndroidStudio2.1, as well as .gradle and .m2 if they exist. You can go this way too:  C:\Users\(%USERPROFILE%)

Step 3: 

Then go to %APPDATA% and delete the JetBrains directory.

Step 4: 

Now delete the any AndroidStudio directories that are in %LOCALAPPDATA% and %APPDATA% that are inside Google folder. Normally here: 

  • C:\Users\(%USERPROFILE%)\AppData\Local\Google
  • C:\Users\(%USERPROFILE%)\AppData\Roaming\Google

Step 5: 

To delete any remains of the SDK, go to C:\Users\(%USERPROFILE%)\AppData\Local and delete the Android directory and Android Open Source Project.

Step 6: 

Go to C:\Program Files and delete the Android directory

Final Step: 

You have to do three extra works. Here are those. 

  • Delete everything from Recycle Bin
  • Click right button on C: drive. Open Properties > General tab > Disk Cleanup. Put tick mark on all items and press Ok > Delete files
  • Open 'Disk Defragment and Optimize". Open by typing it in Run. Now select C: drive, then click on 'Optimize'.