Windows 8.1 upgrade help

So this is the case, my brother has a toshiba laptop with a 40 GB partition for me to use windows 8, today I started to download windows 8.1 and leave my brother with the instructions to do the upgrade, sadly he didnt have my windows account password so he couldnt finish the upgrade. After I got home I turn off the computer thinking that the upgrade would start again but it didnt and the thing is that in my c: drive it shows that the space that the download took for the upgrade is not there so the upgrade should be on aanywhere on the pc and I cannot find it, neither can I start the download again for insufficient storage space, what should I do