My laptop crashed, a little help please!

Hi! Need your help please,, Under the system properties, I had changed the settings under performance from ‘let windows choose what’s best for my computer’ to ‘adjust for best performance’, and then I restarted my computer, it did boot up but up to welcome page only, and a message box displays ‘windows cannot load user profile but has logged on the computer default system’.. I cannot open my computer, help me,, I have many important files in it, will it also be harmed, its an acer travelmate,, many thanks!