My brother has downloaded a executable file from Skin Pack — I believe it was the Mountain Lion IO6 skin pack. He's using an Acer Aspire 553G. And now his operating system won't start (Windows 7). It gets to the BIOS and then goes to load up the OS but the screen goes blank and it just goes back to the BIOS over and over again. He decided to play with the bootup settings and tried different options and got the error message "Operating System not found." Does anyone have any idea how to solve this?