ignoring the ****head who thinks he knows all....
I ended up buying a 500w ATX12V P4 dual fan, low noise power supply.
I crashed the computer before installing it to confirm the problem was still there and to see at what point it crashed during a video conversion.
It made it to 19 minutes.
I changed the power supply and converted the same video, 42 minutes, no crash.
I then created a dvd, which I could not do anymore as the comp would crash everytime at less than 20%.
2hrs 49mins to create a dual layer dvd successfully without crashing.
I have since, loaded up as many programs as I can at once, copied from the dvd-rom to the hard drive, burnt a dvd using the other burner and had winamp running, all at the same time which I could not do before.... again, no crash.
Looks like my problem has been solved.
I am still of the belief that if the cause was my power supply, this may have caused damage to the other parts I replaced, after replacing the ram, it did not crash for awhile and no loner crashed when running photoshop... but still crashed when video converting.
Hope this may help someone else solve their similar issue.
Thanks to those who posted with ideas, as for you PSU GOD...