Windows Vista SP1 error distribution as of Sep 08:
From Windows Internals, 5th Edition

Page Fault - 20.6%
 - 0xA - IRQL_NOT_LESS_OR_EQUAL
 - 0xD1 - DRIVER_IRQL_NOT_LESS_OR_EQUAL
Power management - 17.4%
 - 0x9F - DRIVER_POWER_STATE_FAILURE
 - 0xA0 - INTERNAL_POWER_ERROR
Access violations - 15.4%
 - 0x50 - PAGE_FAULT_IN_NONPAGED_AREA
 - 0x8E - KERNEL_MODE_EXCEPTION_NOT_HANDLED (w/Parameter 1 = 0xC0000005 STATUS_ACCESS_VIOLATION
Exceptions and Traps - 9.8%
 - 0x1E - KMODE_EXCEPTION_NOT_HANDLED
 - 0x3B - SYSTEM_SERVICE_EXCEPTION
 - 0x7E - SYSTEM_THREAD_EXCEPTION_NOT_HANDLED
 - 0x7F - UNEXPECTED_KERNEL_MODE_TRAP
Display - 7.8%
 - 0xEA - THREAD_STUCK_IN_DEVICE_DRIVER
 - 0x10E - VIDEO_MEMORY_MANAGEMENT_INTERNAL
 - 0x116 - VIDEO_TDR_FAILURE
Pool - 5.5%
 - 0xC2 - BAD_POOL_CALLER
 - 0xC5 - DRIVER_CORRUPTED_EXPOOL
Memory management 4.8%
 - 0x1A - MEMORY_MANAGMENT
 - 0x4E - PFN_LIST_CORRUPT
Consistency check - 4.7%
 - 0x18 - REFERENCE_BY_POINTER
 - 0x35 - NO_MORE_IRP_STACK_LOCATIONS
 - 0x44 - MULTIPLE_IRP_COMPLETE_REQUESTS
 - 0xCE - DRIVER_UNLOADED_WITHOUT_CANCELLING_PENDING_OPERATIONS
 - 0x8086 - Stop code used by the Intel storage driver IASTOR.SYS
Other - 4.0%
Hardware - 3.6%
 - 0x77 - KERNEL_STACK_INPAGE_ERROR
 - 0x7A - KERNEL_DATA_INPAGE_ERROR
 - 0x124 - WHEA_UNCORRECTABLE_ERROR
 - 0x101 - CLOCK_WATCHDOG_TIMEOUT (most common w/overclocked systems)
USB - 2.7%
 - 0xFE - BUGCODE_USB_DRIVER
Critical Object - 2.3%
 - 0xF4 - CRITICAL_OBJECT_TERMINATION
NTFS file system - 1.5%
 - 0x24 - NTFS_FILE_SYSTEM