If Apache was installed using NSIS installer it should have left an uninstaller. You should search inside Apache installation directory for executable named unistaller.exe
or something like that. NSIS uninstallers support /S
flag by default for silent uninstall. So you can run something like "C:\Program Files\<Apache installation dir here>\uninstaller.exe" /S
From NSIS documentation:
3.2.1 Common Options
/NCRC disables the CRC check, unless CRCCheck force was used in the script. /S runs the installer or uninstaller silently. See section 4.12 for more information. /D sets the default installation directory ($INSTDIR), overriding InstallDir and InstallDirRegKey. It must be the last parameter used in the command line and must not contain any quotes, even if the path contains spaces. Only absolute paths are supported.