BSOD's are primarily by caused two things.
1) Hardware.
2) Software.
Run the onboard diagnostics software from the hardware manufacturer. If you can't find it, the hard drive manufacturer should have it's own tools or use Seagate's Seatools. Memtest86 is good for ram testing.
minidumps are created when either your system auto restarts due to a crash or when you get a BSOD. you can safely delete them, but don`t delete the folder itself. they do relate to BSOD`s. They are a good source of information that can be analysed.
how to read minidump http://support.microsoft.com/kb/315263