"HELP ASAP" Vista blackscreen w/arrow only after logon

i really need help on my laptop. it's a windows vista home premium. after i log on the screen becomes blank with the arrow. i can move the arrow but nothing else appears. i tried pressing Ctrl+Alt+Del but nothing appears. i even tried restoring it to an earlier time but it didnt change anything. i even went into the registry and changed the value of Shell to explorer.exe but it went back to before after i restart. i went to BIOS and put it to default & nothing changed again. i tried safe mode:blackscreen with cursor too; last good known config: nothing changed.i tried solving it many ways according online but it didnt make a difference. the problem was cause by a windows update but i dont know how to fix it. "the only thing that worked was the SHIFT. i pressed it 5 times and i can open control panel, my computer, and stuff like that but i cant open task manager. please help because the laptop was just bought for a couple of months. please help & thank you

Hello,

It seems that your Windows is corrupted. You can perform repair with your recovery partition. What is the brand of your laptop?