Let me ask if the Electrum 3.3.8 is a portable version?
If yes then the 4.0.9 is already in your system you must look for .exe file and make a shortcut on your desktop.

Or if the 3.3.8 is not portable you can uninstall it first before you install the latest version but before you install make sure that you have wallet file backup that you can find mostly on \Users\YourUserName\AppData\Roaming\Electrum (or %APPDATA%\Electrum). Once you have the backup wallet you can proceed to uninstall 3.3.8 then download the latest version to the original electrum website this is the original one https://electrum.org/#download be careful on fake Electrum websites.

After you install you can now import your wallet file to the same location (\Users\YourUserName\AppData\Roaming\Electrum) and then open your wallet or use seed backup if you have.

Then try to restart the PC/laptop again let's see if your the Electrum version still the same after reboot.