Good MSDN articles about DbgPrint under Vista (new way to use DbgPrint!)

IHVVIDEO Video driver
IHVAUDIO Audio driver
IHVNETWORK Network driver
IHVSTREAMING Kernel streaming driver
IHVBUS Bus driver
IHVDRIVER Any other type of driver

http://msdn2.microsoft.com/en-us/library/ms792789.aspx
very good article

http://msdn2.microsoft.com/en-us/library/ms792790.aspx
the following two function calls are identical:

DbgPrint ( Format, arguments )

DbgPrintEx ( DPFLTR_DEFAULT_ID, DPFLTR_INFO_LEVEL, Format, arguments )

The component for this routine is DEFAULT. Because you have not set
the DEFAULT component filter mask, it has a value of 0x1. When this
mask is combined with the importance bit field by using an AND
operation, the result is zero. So the fourth message is not
transmitted.