1. windows update problem
Windows Modules Install Worker occupies CPU and finally makes OS stop

2. in Browser, export bookmarks and save in Document. bookmark.htm is made.

3. backup folders such as Downloads, Documents, Pictures. (20 min)

4. download windows ISO and make a bootable USB from MS support site searched from google by "windows iso usb"

5. go into Bios by fn+F2 during booting, change booting order to make USB booting the first

6. install windows (20 min)
6.1 select 101 keyboard type 3
6.2 find IE by finder on the left bottom and fix it on taskbar
IE 11 does not show menu in default -> right click on black area and select menu collection
File > import > import bookmark.htm
6.3 Bios booting order is automatically reset to start from main drive.

6. windows update (15 min)

7. copy back from backup folders

8. hancom office install (15 min)

9. if printer problem like duplex printing -> reinstall the driver

9. MS office install