Why do you want to copy that HTML file to LENOVO? Instead you can request it in your browser (on LENOVO) via the IP of ASUS:
http://192.168.20.5/subfolder/myfile.html (or similar).
If you want to run and request HTML files via http Protocoll from LENOVO, you need to install another Apache onto LENOVO. You cannot request a file from LENOVO from Xampp on ASUS. That does not work. BUT: if you dont need PHP but only HTML at all on LENOVO, you also could request the HTML in your browser NOT using http Protocoll, but instead opening the HTML file direct from the local (LENOVO) path. That is called "file:" protocoll and would look like this in the browser:
file:///C:/anyfolder/somewhere/on/lenovo/myfile.html
You can achieve this also by simply double clicking on myfile.html in an Explorer OR use "Open...." menu entry in the local LENOVO browser. In the case, you run a copy of HTML stored on LENOVO, you must apply 192.168.20.5 as database server in the xmlhttp code. You cannot use "localhost" or 127.0.0.1 there (as you do on ASUS).
But still, what is the idea of running a copy of myfile.html on LENOVO? Why not running
http://192.168.20.5/subfolder/myfile.html instead (in that case you dont need to change anything, probably you might add certain rules to the ASUS firewall, as the Windows firewall usually blocks incoming requests).