Edit:
I found an easier way to solve this problem, this was caused on my laptop by pressing fn button with the + key on keyboard so pressing fn and - key reverts back to the smaller original windows font.
So I finally found the solution , you should change the registry key to the default value by the following steps:
You should copy the content of this section & put it in a notepad file with extension .reg then run it , it will revert the windows fonts to the default
"Window Metrics" Registry Fix (Restore defaults)
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics]
"IconTitleWrap"="1"
"Shell Icon Size"="32"
"BorderWidth"="-15"
"CaptionFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\
00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"CaptionHeight"="-330"
"CaptionWidth"="-330"
"IconFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\
00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"MenuFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\
00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"MenuHeight"="-285"
"MenuWidth"="-285"
"MessageFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\
00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"ScrollHeight"="-255"
"ScrollWidth"="-255"
"SmCaptionFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,\
00,00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"SmCaptionHeight"="-330"
"SmCaptionWidth"="-330"
"StatusFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\
00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"AppliedDPI"=dword:00000060
"PaddedBorderWidth"="-60"
"IconSpacing"="-1125"
"IconVerticalSpacing"="-1125"
"MinAnimate"="0"