Loaded Win 10 OS from bootable USB and this caused it to lose previous Win 7 OS to run it

[WPCentral Question]

MY trusted laptop ran Win 7 Home premium but would not display the windows 10 icon so following MS's instructions downloaded win 10 OS and installed it from a pen drive. Well something glitched during install and now it says "missing operating system". MS tech said must reinstall Win 7 OS from Acer who holds the license. Acer says my laptop is out of warranty and to install win 7 again have to pay more than a direct license for clean install of Win 10 from the MS store. And to me the warranty is for thehardware which works just fine- no issues. Asked MS why had to pay for Win 7 OS reinstall when it is their product and their answer is that it is now unsupported, but get this the install of Win 10 was supposed to be a free upgrade so this in my mind is rip off that MS should take responsibility for. MY laptop runs on a i7 processor with 3 GB of RAM and came with win 7 preinstalled when I bought it new from MIcrotic a store in 2011.