Debugging a UMDF driver on BOOT in Vista

I’m trying to debug a scenario which a happens at system boot.
My driver is written in UMDF and runs on Vista, so I cannot use the Log Boot option in DebugView.
Does TraceView support logging at boot time? If so, how is this option enabled?
If not, what other way is there to know what happens at boot time?
I’ve tried writing to a file, using standard user-mode C++ functions (fopen, fprintf and fclose), but the file fails to open. Maybe I should use other functions in order to write to file from the driver?