BSOD multiple errors, error 0x00000050 and error 0x0000003B

Had a BSOD on Sunday. Took the sides off the computer to find the heatsink caked in dust. Cleared that out with some compressed air and seemed to do the trick just fine. Computer fan running much quieter too then.

All fine on Monday and then cranked the PC up this evening and BSOD again. Couldn't get Windows to start, so tried removing RAM and then removing all hard drives except my boot drive containing Windows. Set up is SSD with Windows on, second SSD with programs on, HDD for files and data and second HDD for backup; that set up has been running fine for some time.

Have managed to get Windows to load and no BSOD currently, with three drives plugged in and the main HDD for data NOT plugged in. Not sure if that drive is the common problem.

Some BSOD messages I have seen, before it vanishes, include PAGE_FAULT_IN_NONPAGED_AREA and REGISTRY_ERROR and SYSTEM_SERVICE_EXCEPTION

Any help and advice much appreciated. The diagnostic data was run without said HDD plugged in.

Brief update.....
PC still running but trying to shut down, I get a Windows Explorer has stopped working error, as below. Could this be linked to the other drive not being plugged in? The unplugged drive contains my 'Desktop' so I wonder if this is confusing Windows somehow. Only way to shut down seems to be to just power off.

Problem signature:
Problem Event Name: APPCRASH
Application Name: Explorer.EXE
Application Version: 6.1.7601.17567
Application Timestamp: 4d672ee4
Fault Module Name: SHELL32.dll
Fault Module Version: 6.1.7601.18762
Fault Module Timestamp: 54dd89c7
Exception Code: c0000005
Exception Offset: 0000000000426c50
OS Version: 6.1.7601.2.1.0.768.3
Locale ID: 2057
Additional Information 1: 5494
Additional Information 2: 5494a2554492f54f142318b9d76e48db
Additional Information 3: 4bfa
Additional Information 4: 4bfac08edc6eca7a0addb6c998a3f922

Hiya and welcome to SevenForums!

Code:

BugCheck A, {fffff900008d1ee9, 0, 0, fffff80002ad41dc}

Probably caused by : win32k.sys ( win32k!AllocThreadBufferWithTag+24 )

Followup: MachineOwner

Hmm, re-install Windows as your getting 0x51 errors because 0x51 errors are registry related errors.