it happens every time i start my PC. The hang is at the XP logo screen where the blue progress bar continually cycles and before this i also hear a tickling sound inside my case.i always hit the restart button everytime this happens and afterwards it prompts me whether to restart windows in normal mode, safe mode etc.i choose normal mode and that's it my pc runs smoothly again.my problem is only during the start up..sometimes it also hangs when it's already at my desktop screen 
what could be the problem is it software or something else
help will greatly be appreciated 
what could be the problem is it software or something else