INT 05 is range exception but the c0000005 code is reoprted by a normal GP fault. Phil, what exactly occurs on the "chernobyl screen"? Do you get a line like TRAP D or TRAP 5 something like? Does the output to the chernobyl screen hang during outputting the text (that's very bad)?
At any rate, try to comment out drivers in the CONFIG.SYS Most likely, you will need your CD and start the console from it. Try to comment out as much drivers as possible - all network, multimedia, PSD, APM and so on. Leave only video and HD. If you pass then start uncommenting "groups" - network, and so on. If you don't pass even with bare bones (HD and video) then the problem is hardware related most likely.