my problem is when i switch my notebook what comesout is "windows Error Recovery"

i have 4 choices

1. safe mode

2. safe mode with networking

3. safe mode with command prompt bla bla bla...

4. start windows normally.

when i enter no 4 what comes out next is "ows failed to start. A recent hardware or software change might be the cause"

then i press enter again, the 4 choices appears again.

what ever i do it just turns back.

what should i do?