Windows7 Blocks at Welcome part

Hi
i have a windows7 64 bit powerful computer and yessterday i cleaned him (hardware and software) and did a defragmentation using Smart defrag 2.2 and also used other programs to fix errors! the thing is that after all that work i turned the pc off and it started doing those windows updates.. there were 57 and then it turned off normaly but the next day (today) i tried to turn him on but he gets stuck on the Welcome part after typng my windows' account username password... i NEED help urgently please!
i also installed a program that changes my windows log in background.. could that be the problem?

thank you :(

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