Recently, I have been experiencing hard crashes on my computer, which I have been using for over two years now. What happens is that I see a flash of blue screen and then my system reboots. After the inital shock, panic, and trying to remember what files I had saved/not saved, I shrugged it off as a one-time thing and continued working. After the third time, I decided I should take a closer look at the problem.
I discovered that a minidump file is created when your system crashes, if you have it set up to do so. Create the minidump file, that is. Typically, the dump files are located in C:\WINDOWS\Minidump. But, you can't just look at the dump file in a text editor, you have to use the Dump Check Utility which is part of the Windows XP support tools. Needless to say I didn't have the support tools installed. I installed the tools which end up in a default directory of C:\Program Files\Debugging Tools for Windows (x86). I found this helpful KB article that tells you everything you need to know about minidump files and how to read them.
I ran the graphical version of the Dump Check Utility called windbg.exe. If you're reading the KB article and are stymied by talk of debugging symbols, don't worry, I just ran the following command and it worked for me (just be sure to modify the path of the dump file which is the last parameter):
windbg -y srv*c:\symbols*http://msdl.microsoft.com/download/symbols -i c:\windows\i386 -z c:\windows\minidump\Mini072808-01.dmp
So I discovered what app seems to be causing the problem and since this started happening after an upgrade to XP SP3, my hunch is that there is some sort of incompatability between the upgrade and the offending app. Although a bad memory board is not out of the realm of possibility either. I'll keep you posted on further investigations.