Hello Ax
Thank you for your reply and the instructions that even an idiot could follow.
When I went into the event viewer I found many errors showing

(frightening really) but this one looks to me to be the most likely. I could be miles off here, of course.
If this is a red herring then I will indeed disable the restart and await the next BSOD.
Thanks in advance.
Nelclaret
Event Type: Error
Event Source: System Error
Event Category: (102)
Event ID: 1003
Date: 02/02/2007
Time: 09:44:25
User: N/A
Computer: DESKTOP
Description:
Error code 100000d1, parameter1 00000007, parameter2 00000002, parameter3 00000000, parameter4 f89ffe88.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 53 79 73 74 65 6d 20 45 System E
0008: 72 72 6f 72 20 20 45 72 rror Er
0010: 72 6f 72 20 63 6f 64 65 ror code
0018: 20 31 30 30 30 30 30 64 100000d
0020: 31 20 20 50 61 72 61 6d 1 Param
0028: 65 74 65 72 73 20 30 30 eters 00
0030: 30 30 30 30 30 37 2c 20 000007,
0038: 30 30 30 30 30 30 30 32 00000002
0040: 2c 20 30 30 30 30 30 30 , 000000
0048: 30 30 2c 20 66 38 39 66 00, f89f
0050: 66 65 38 38 fe88