Pc does not shutdown blue screen appears after turn off

[zeeboogii]

i cant restart my dell vostro 400 every time i turn it off or restart it a blue screen apears system fans are still working
my pc is vostro 400 dell 3.0 c2d e8400 4gb of ram 250gb of hard drive
if any one could help i shell be thankful

 

[killersquirel11]

What OS?
Does it show the BIOS screen?
Is the blue screen before or after the computer restarts?
If it blue screens while booting after restart, does turning it off then back on again make it work?
Is there text on said blue screen?