OK,the tale from the start. My bad, I didn't think to mention all of this.
I built it and reinstalled the OS clean, then did a virus check because of the cascading crashing programs, and found a virus that AVG had not caught, plus several dormant ones in files I had downloaded and not opened. So I ran Avast! through all of both drives three times, and DrWeb through it all three times, and not just through the 2 hard drives, but my back up external hard drive and my USB sticks. Then I reinstalled the OS again. (DrWeb destroys viruses but is not an AV program)
I must have reinstalled Win XP Pro about 5 times in all, including reformatting ALL of both hard drives each once, and the C partition at least 4 times. I then moved to Win 7 Pro in the hope it was the OS being a bit old for the new DDR3 stuff that was the problem. /shrug.. you never know, and I wanted to migrate anyway. I got a Student copy of Win 7 through the college I am at.
Since then I have done a clean reinstall of the Win 7 OS at least 3 times. So it has been thoroughly reinstalled fresh several times and the error has shown up as the same, though the messages in Event Manager and on a BSOD have been varied. And I haven't had messages that point to anything specific - they are pretty general like Explorer has fallen over, or it couldn't find something..
Somewhere in all that I found out about the problems with the way the HIS and other brands of the Radeon video card I had starting up slowly in 2D mode was causing crashes, so I returned it and changed it for an Nvidia video card, the 250 GT. That got rid of a lot of problems.
I have run it with Opera instead of Firefox as it was suggested that the browser might be the problem. It was the same with Opera.
I have run it with minimum programs on, no change. I have not tweaked it as I usually do, except to make the Services match those on Black Viper's site. Again no difference. It starts up and crashes instantly I try to open my browser or start up the not-starting Windows Defender. So it isn't incompatible programs.
I did have something new this morning, though, after an evening watching a couple of movies and TV shows ... When I started up it went straight into the Recovery program and I chose to let it Roll Back to last good option, which failed. So I put in the Win 7 CD and told it to boot from the CD with the intention of reinstalling fresh by reformatting the C partition, but it loaded Win 7 normally for some reason.. I have no idea why, but I got no Install screen, so I have left it to see how it behaves. It has been as stable as I could want, even playing Mass Effect 1 this evening.
It is possible that all the crashing this time around has damaged the OS yet again, and it now needs yet another fresh install. I have to admit I decided that since I was closing down almost instantly after the first boot up, and not starting any programs until after the 2nd cold boot up, that maybe it wasn't getting damaged. But after it starting normally, I can restart it as often as I want, or even close it down for 2 hours and it starts normally with no problems at all. It only shows the problems if I leave it off for 6-8 hours.
Dark Mantis, there is a big difference between being not comfortable doing a procedure, and ignoring advice. I know my limitations and I would prefer to put it into a shop for repair rather than risk damaging the components myself. At this point IF they are faulty, I can recoup the money or get a replacement. If I damage them by taking it apart and reassembling them, and there is always that risk when you remove components, then I am out a whole PC. I should add I am unemployed and a student retraining at college right now as my UK teaching qualifications are useless here in the USA. So money is scarce.
I already had to shell out an extra $200 on a new chip as my son's friend, who was supposed to be only taking my last PC innards out of my case and putting them in the new case I bought my son for his 25th birthday, started making up my new rig before I could stop him, and mashed my chip the wrong way into the motherboard. And I do mean mashed.
I couldn't even say anything as we were working on another table next to my son who was table top gaming with other friends of his at the time..
absic115, I had wondered about the PSU size myself, but the PSU is powerful enough because when I changed the video card, I got it from Fry's Electronics and asked to speak to a rep who was a PC builder. I then went over my components with him to check my PSU was adequate and he assured me it was more than powerful enough to deal with that motherboard and video card. The only other things I have plugged into the mobo are my Audigy 2 sound card and the memory. All parts apart from the Nvidia video card came from NewEgg not Fry's, so he had no reason to say the PSU was well up to the job if it wasn't because he could have tried to sell me a new PSU at that time. Not just that, but before I bought the components I checked with the friend who usually built my PCs till I moved South. He said I was well within the specs with that one, and even suggested getting the 3 x 12v rail model.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371016 It is about $70 worth of PSU, actually. And here in South California, with our high cost of living, and me being unemployed, that is quite a lot for me.
Personally I am thinking it is a faulty motherboard now, or perhaps the fact it is G-Skill memory and that board has a dislike of G-Skill. Anyway, since my money is tight, trying to replace either the PSU or the memory on spec is not sensible when I don't know if either is at fault. It makes more sense to put it into a shop where they can test everything.
I do thank you all very much for your time, and for your suggestions, and I have tried what you suggested, apart from rebuilding it outside the case. I will try yet another reinstall of the OS tomorrow, on a reformatted C drive yet again, just to be sure it is clean. If I still have problems, I give up and will let the pros with test equipment handle it.
Again, thank you for your help, it has been very much appreciated.