Questions about dell inspiron 1520 laptop boot system with cd external

[Guest]

I have a problem about laptop inspiron 1520. my CD-ROM device is broken and I'm working with an external CD-ROM. But I can not boot the machine and install Windows.
Please guide me please.

 

[snakebitex]

Hello.
1.Plug your external usb drive.
2.Go to bios and change your bootable device to usb external device.
3. Boot from cd
4. Install