I was finally able to get Windows 8 installed on a USB drive and got it to boot up. The installation screen came up and gave me two options; Upgrade or Custom. I tried to do custom first, to which it asked me where I wanted to install it. It gave me about 8 different options of places, all of which it said it couldn't install on cause there wasn't enough room... Any ideas on what to do?
Sorry to butt in, but if the laptop originally came with Windows 8 and the OP has upgraded it to Windows 10, isn't there a recovery solution within Windows 10 to allow you to downgrade back to Windows 8 without recovery media?
Plus, if you directly try to reinstall Windows 8, surely the key is now invalid as it's already been converted to a Windows 10 key?
EDIT:
Okay scratch that, the downgrade option is only available for up to one month after your upgrade from Windows 8 to 10: How to downgrade from Windows 10 to Windows 8.1 or 7
I realise you scratched that but essentially you are right although as you have found out that downgrade option only lasts for 30 days. Having said that Microsoft do, now, supply a "Media Creation Tool" for Windows 8, 8.1 and 10. You can also get media for Windows 7 from Microsoft but that isn't quite so visible as the others. Once the Product number has been registered with Microsoft for either Win 7 or 8 that product number is then used for Win 10. It doesn't change to a Win 10 number. There are no product numbers supplied with Windows 10. Problems can arise if your computer is using UEFI rather than standard BIOS. Then the product number is embedded and isn't shown on a little blue sticker like the old days. Having said that Belarc or a similar program will display the product number but you shouldn't need it as during the Windows 10 installation process it should pick the number up automatically. Problems have arisen where an update hasn't been recieved and the product number hasn't been registerd then Windows wont activate then you have to contact Microsoft to sort it out. That is an experience in itself LOL.
I also suspect that somwhere along the line things have got mucked up anyway so possibly the only option is a clean install anyway. This is, by far, the better option anyway. Doing the upgrade from Win 8 or whatever drags all the crap along with it from the old intall. OOHH lots of anyways in there sorry LOL.