What is the Blue Screen of Death and what could be it's causes ?

Sometimes bad or flaky memory (RAM memory, not your hard drive) can cause seemingly random system crashes. If you have just the right combination of programs open and system memory in use, and your computer tries to access a "bad spot" on a RAM chip, the results can be unpredictable. Or they can be the Blue Screen of Death. You can try replacing your RAM sticks one at a time to see if the problem goes away. This involves opening up the system unit and looking at scary wires and stuff, so for some people just living with the problem may be a workable option.

More likely, you have a software problem. Some programs just don't get along... they trample on each other's memory spaces and confusion (or the BSOD) results. And it seems that Windows just gets old and cranky the longer you have it installed. You may solve the problem by using the System File Checker, or if all else fails, by 

re-installing the Windows operating system and/or your software packages. If the problem seems to be limited to one particular program, try re-installing just that one first.

Spyware or a computer virus can also make strange things happen.