Worthy of note is that the Windows 7 procedures using the Windows 7 USB/DVD download tool can only create a 64 bit bootable USB if using it on a 64 bit machine. On Windows 8 and 8.1, you can only download an image that matches the bit setting of the downloading system. These can be severe limitations if you are wanting to change from a 32 bit system to a 64 bit one.
A way around these limitations for Win 7 is rather obvious. Find a mate with a 64 bit machine and do the lob there. For the Windows 8 and 8.1 downloads do not create a USB when asked. Opt for creating an ISO and then find a mate with a 64 bit machine and use the Windows 7 USB/DVD download tool. It will work OK on Win 8 and 8.1 .