Your USB mouse should have been ok as such things are PnP or plug n play. When it means remove all USB hardware it's meaning stuff like printers and external drives.
Can you list your system spec although I doubt it's the actual build causing the problem. Personally I'd make sure that in your bios, that USB k'board and mouse are enabled (if you don't see such a setting then it's likely enabled by default). I'd also make sure your system bios is the latest version. I'd then run through the install again leaving your mouse and k'board attached..