If u search for something like that u can see that i have had that same problem, but not once twice!!! windows freezes on the logo, just like u said, and keeps running, and the only way u can log onto ur computer is safe most with networkin or safe mode..yes, the only way to fix that is to reformat...i don't know how mine has happened these last 2 times, but i know the last thing i did before i turned off my computer and it did it was running Ccleaner issues thing.. so for now on i always save my registry files when i delete CCleaner issues and if something ever works i will get into safe mode and put them back..
i hope at least
hope that help me man, sry that i can't tell u what can fix it without reformatting but i tried everything that u can thing of myself and nothing..
hope everything gets worked out for u.