The primary reason is that some software or driver failed. There is NO do-this and it will work cure. There is also the issue of PESTS (virus, spyware) and the damage they inflict.
Sometimes the owner will install some software and cause the issue. Fix? Uninstall that software.
More at this link -> http://www.techspot.com/vb/all/windows/t-46739-BSOD-when-going-and-coming-from-sleep-mode.html lists the usual resources and notes.
My computer locks up when I try and put it into standby, manually or via my Compaq keyboard 'sleep button'. What can I do to sort this, other than reformatting. Even when I have my computer setup to automatically go into standby after an hour - it locks up and doesn't go into standby.