Install Win 7 na Acer E1-510 (problem)

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Dobio sam Laptop "Acer aspire E1-510" s tvornički instaliranim Win 8. Navikao sam na Win 7 i htio bi ih instalirati na njega. Našao sam upute ovdje kako to napraviti ali ne ide mi.
Sve sam radio točno prema navedenim uputama:

1st of download these bios file ( Click Here To Download Bios ) bios also available on official site
1. format USB drive as Fat32 File System
2. extract all files from bios to the flash drive
3. plug in the AC adapater, & USB inside your lapotop
4. power on laptop & hit F12 key
5. select usb boot and press enter
6. then type C: hit enter
7. then type flashS.nsh (S is capital)
8. it will start bios update
9. after bios upate you can switch efi boot mode to legacy mode and install windows7

Zapinje nakon 5-og koraka:

Pojavi se crni ekran gdje piše:
EFI SHELL VERSION 2.31
DEVICE MAPPING TABLE
SHELL>

Ja upišem C: i pojavi se:
SHEL: INVALID MAPPING NAME - C:
EXIT STATUS CODE: NO MAPPING

Zna li ko u čemu je problem