Hi,
No problem, I'am a window user to.
You need a program like winspc to place the macOSXUpdCombo10.4.9Intel.dmg file in the right place on your apple download link
http://winscp.net/download/winscp417setup.exe
open the program on your pc choose session
loggin to your apple tv
adress is ip adres of your appletv (you can find it on your apple tv under general info) fill in adress without DHCP before it
user name: frontrow
password: frontrow
copy the macOSXUpdCombo10.4.9Intel.dmg into the... frontrow\Documents Foler (Create Documents folder if it's not there)
exit program
No go to to your television and your apple tv choose nito tv
Choose settings then instal software then smart installer.
Rember don't connect anything in to the usb port
Atv is starting to update "thinking"
After the update you can plug in a usb drive
Start XBMC
Your new drive must know be visible under Volumes.
let me no if it works for you
good luck
ps thanks davilla for the correction! I have changed it know!